Narrator: Trekking is all about taking the road less traveled, connecting to nature, to history, and culture, one very literal step at a time.

The view is infinitely more satisfying when you've had to work hard to reach it, and the sense of freedom, absolute.

Every journey made by foot holds the promise of a grand adventure, the chance to transform the way we see the world and even the way we feel about ourselves.

From the highest mountains to the wildest jungle realms, these are the world's greatest treks.

[water splashes] [plane humming] [helicopter whirring] [vehicle rumbling] [boat roaring] One of the greatest joys of trekking, over and above other forms of travel, is just how immersive the whole experience can be-- feeling the incline of a mountain in your muscles or the howl of the wind against your skin.

[wind whistling] And there are few places in the world where this truth resonates with more clarity than the Andes.

The Andes is the longest chain of mountains in the world, home to tens of thousands of kilometers of ancient trails, many of which were blazed by the mighty Incas.

The Incas were a Native American people who rose to conquer and control one of the greatest empires ever known.

Between the 13th and 16th centuries, they held court across western South America, from quito in the north to Santiago in the south.

They worshiped the Andes as both the home and manifestation of their gods, and built citadels and temples throughout the mountains to appease them.

Machu picchu in peru is by the far the most famous.

Built in the 1450s, it was connected to cusco, the capital of the Incas, by the inca trail, which, having outlived the Incas themselves, has become one of the most popular treks in the world.

The sacred entrance to this fabled lost city is a 43-kilometer paved stone pathway that winds up and down a series of passes before reaching a campsite that's just shy of sun gate.

Nearly a million people visit Machu Picchu every year, two and a half thousand every day, and while most will travel most of the way on public transport rather than on foot, those who do trek the whole way in get to be the first onsite, drinking in all the wonder that surrounds them before the hordes ascend.

The reason why the Incas abandoned this secret sanctuary just a hundred years after it was built remains a mystery, and the fact that it now lies in ruins only heightens its mystical aura.

Many historians believe the site was not only used for sacred rites and rituals, but for studying the stars.

The intihuatana, an altar-like structure in the complex, has a stone slab that served as a sundial and calendar.

It was said to anchor the sun to the Earth during its passage through the sky, and local guides claim it grants a special energy to those who approach it.

Machu Picchu is one of the most famous archeological sites on the planet, but it's not the only lost city in Peru.

There are others that can be reached on foot via walking paths that are no less spectacular but infinitely less crowded than the Inca trail.

Where authorities will issue 500 walking permits a day to trekkers bound for Machu Picchu, the 60-kilometer trail to Choquequirao would be lucky to see that many people in a year.

This is the toughest but perhaps most rewarding of all the trails forged by the Incas, the one that delivers on the promise of leaving those who have ventured along it with a powerful sense of having stepped back in time.

It's far easier to gain an insight here into just how deeply the Incas felt about their mountains, for the silence alone invites reverence and contemplation.

The hardest section on this five-day hike is the ascent from the Apurimac river to the ruins of Choquequirao via a series of punishing switchbacks that seem to go on forever.

Hiram Bingham, the British professor and explorer credited with rediscovering the ruins of Machu Picchu, was also led by local farmers to Choquequirao, a far larger complex of houses and temples that's still being unearthed and cataloged.

It too was built in the 15th century and is now thought to have been the final refuge for the Incas as they attempted to resist the Spanish.

Choquequirao's most iconic feature is the limestone and granite stairway that ascends to the main plaza, inlaid with llamas fashioned from contrasting white rocks.

While the ruins in Choquequirao and Machu Picchu get the emperor's share of attention, their settings are equally wondrous, and taking the time to explore them on foot is the best way to sense their sanctity, to reap a deep sense of achievement from the journey and fulfillment from the final destination.

Some of the most highly regarded treks in the world owe their renown to history and a nostalgic desire to retrace journeys made by people we admire or revere.

Every year, some three and a half thousand trekkers set out to tackle the notorious Kokoda track in Papua New Guinea, following in the footsteps of a battalion of young soldiers caught in the bloody turmoil of World War II.

Many of the people who sign up for this trek are Australians paying tribute to their grand and great-grandfathers, who, over four months in 1942, waged a series of brutal battles along the Kokoda against the Japanese imperial army.

At the time, the Japanese were planning to capture Port Moresby via the Kokoda trail, so they could then use the city as a base for attacking the Australian mainland.

Most of Australia's armed forces were engaged in Britain's war against Nazi Germany, so the task of defending the country from this remote frontline in the pacific fell largely to the inexperienced soldiers of the 39th militia battalion.

They were young, poorly-trained, and ill-equipped, shipped out in haste to defend Kokoda and its strategic airstrip from the advancing imperial army, setting the scene for a bitter campaign that would etch itself into Australia's history and national psyche.

No longer a battlefield, the Kokoda is still quite treacherous, a narrow trail that roller-coasts its way across the imposing owen stanley ranges.

Not for the inexperienced or, for that matter, the fainthearted, the length of this trek is measured by the number of days it takes to complete rather than the actual distance.

It can be conquered by the ridiculously fit in less than 24 hours, but most trekkers prefer to spread their suffering over a week and a half.

The track can be traversed in either direction, but more often than not, it's tackled north to south, setting out from the village of Kokoda.

The first hour or two of the trek in this direction is relatively flat, which allows those undertaking the challenge to get accustomed to the intense heat and humidity before having to confront the first of many uphill slogs through the jungle.

This is harsh and unforgiving terrain that, with one short downpour, can turn the slippery, muddy trail into a quagmire.

A memorial at Isurava, a village most trekkers reach by day two, serves as a somber reminder of the even greater hardships those brave aussie soldiers endured as they fought to hold off the enemy in the jungle and the qualities that sustained their resolve even when they were wounded or physically weakened by hunger and tropical disease-- courage, endurance, sacrifice, and mateship.

These four words still define the spirit of Kokoda and spur those who have come to honor the fighters and the fallen along.

It's difficult enough for most people to trek through this landscape burdened only by the weight of a small day-pack.

So it goes without saying that day after day, their respect for the World War II soldiers who fought here deepens, as does their admiration for the guides and porters who are following in the footsteps of their own local heroes, the legendary fuzzy wuzzy angels, local stretcher-bearers who carried so many wounded soldiers off the Kokoda and out to safety.

Eora Creek, which is the destination most groups reach at the end of day four of the trek, was the site of the bloodiest of all the battles waged along the Kokoda, a costly clash that took the lives of 99 Australians and wounded 192.

It's still possible to find remnants from that skirmish in the jungle today, including an ammunition dump left behind by the Australian soldiers.

When all was said and done, 625 Australians had been killed on the Kokoda, and more than 1,600 were wounded.

But losses on the other side were far greater.

More than 10,000 Japanese soldiers died.

The highest point on the track, at 2,190 meters, is reached on day five, when the trail skirts around the summit of Mount Bellamy.

But that doesn't mean for a moment that it's all downhill from there.

The valleys only seem to get deeper, and the track, if anything, steeper.

The only flat part of the trail between eora and owers' corner at the southern end of the Kokoda track crosses the open plains of myola.

This was an important resupply point for the Australian soldiers in 1942, with food, ammunition, and other supplies dropped from aircraft onto the open field.

There's no need for that now, of course, for everything that's required to keep today's bone-weary trekking groups relatively comfortable is packed in and packed up and packed out.

Evening campfires warm more than the food that's served up at the end of each day.

They provide an opportunity for those undertaking the arduous journey to share their personal stories, to at least momentarily forget about blisters and aches and pains and enjoy the camaraderie of newfound friends, forging bonds that in no small way echo those that formed between the soldiers and their celebrated guardian angels.

The dozen villages en route add another dimension to the whole Kokoda experience and provide a chance for the hardworking guides and porters to unwind but not necessarily relax.

That's a trait that doesn't appear to be coded into their dna.

[people cheering] as soon as the game's over, it's back to work, pushing onward and upward over brigade hill towards the finish line at owers' corner.

The Kokoda track, all 96 kilometers of it, is grueling to the bittersweet end.

The mud, the heat, the mosquitoes, the leeches, the boots that never dry out, all of it is unrelenting.

But the payoff for rising to the challenge that this demanding track presents is finding that you do have what it takes, even when it takes all you have.

[people clapping] [people socializing] many people throughout the world see mountains as symbols of their culture or faith, and since ancient times, have sought to acknowledge their importance by making pilgrimages into their sacred realms... [man chanting] Ritualized journeys that promise to transfix and transform.

For some, these spiritually-motivated treks are all about redemption or penance, but for others, a pilgrimage provides a rare opportunity to connect to something more meaningful.

Surrounded by the beauty and power of nature, they gain new insight into themselves.

3,776-meter Mount Fuji in Japan has been an object of worship and destination for pilgrims for centuries.

Venerated as a stairway to heaven and a place where deities dwell, it's sacred to many Buddhists and followers of shinto, the traditional religion of Japan.

With its near-perfect symmetry linking heaven and Earth, Mount Fuji has often been used to symbolically unite the people of Japan, in times of war and peace.

So any climb they make towards its summit speaks to their sense of nationalism as much as it does their respect for the divine.

Shinto shrines skirt the base of Mount Fuji and are dotted along the Yoshida trail, which zigzags its way from the road-head up to the top of the mountain.

They serve as a reminder to many of the deeds of the original pilgrims, Buddhist priests such as Nichiren, the founder of a sect that bears his name, who spent a hundred days on his own meditating at this site during the 14th century.

While the lower slopes of the mountain are well-vegetated, the upper reaches are totally barren, massive slopes covered in volcanic rubble that need huge retaining walls to hold them in place, thwarting most but not all runaway boulders and landslides.

[whistle blows] climbing Mount Fuji is still seen by the faithful as an act of purification, but with 300,000 people each season setting out to reach the summit, it also requires the patience of a saint.

Many trekkers try to time their ascent to arrive on the summit at sunrise, but that is just as glorious a spectacle to witness from anywhere high on the mountain should you chose to avoid peak hour on the peak.

On the downside, heading up to the summit later in the morning will pit you against the tide, a tsunami of humanity that can overwhelm at every turn.

It's difficult for western trekkers to come to terms with Fuji's ever-present crowds and commercialism, for this isn't the norm on trails elsewhere in the world.

But once they're on top of Fuji, gazing out at that remarkable view, many say they experience a zen-like state of intense contemplation and solitude, a moment where they feel connected to Japan and the landscape of the mind within.

For many keen walkers around the world, the key to a truly great hike has little to do with history, religion, or culture.

The all-important element driving their quest for adventure is wilderness, pristine, untouched places where nature still reigns supreme.

[waves crashing] Ask just about any Australian bushwalker where they would go to get away from it all, and nine out of 10 would shout loud and proud, the island state of Tasmania.

The wilderness down under down under is more than a national treasure.

It's a recognized gem around the globe, with 20% of the island a celebrated world heritage site.

There are places in this primordial landscape that have never seen the slash of a machete or even felt the footfall of a human intruder, adding to the sense of awe they inspire.

There are dozens of similarly wild destinations that can be accessed on foot--great multi-day hikes that wind their way over huge, hulking mountains or slip quietly into the bush.

Iconic treks such as the one that leads to the summit of cradle mountain in the cradle mountain-lake St.

Clair National Park are a challenge in any season, but the neighboring walls of Jerusalem National Park is infinitely more remote.

[bird squawks] There isn't even a road leading into this wild, alpine area.

It's a four-hour hike just to get to the trailhead.

Even those on guided four to six-day walks in the park need to be entirely self-sufficient, but chances are they'll have the place entirely to themselves.

This is real man-versus-wild country, the sort of place hardcore wilderness survivalists can pit themselves against the elements.

Even finding the route can be difficult, as ironstone deposits in the region can affect compass readings.

With key landforms in the park bearing biblical names such as Herod's Gate, King David's peak, and Lake Salome, hikers could be forgiven for thinking they'd stumbled into some earthly version of paradise.

But make no mistake, when the weather changes here, it can quickly turn into hell.

Wildfires can race through the bush in the summer, and in winter, the whole plateau can be blanketed in snow.

The three standout features in this ancient, glacial landscape are the geology, the flora, and fauna.

The overall grandeur of the scenery will impress-- huge dolerite mountains that pushed their way up through the Earth's crust 165 million years ago, and between them, thousands of lakes that were scoured by ice age glaciers.

Many of the larger conifer forests that used to be a feature of the park were burnt out in the 1960s, but alpine bolster heaths, or cushion plants, are no less captivating-- hardy, compact mats of tightly-packed alpine flowers that have adapted to the altitude and weather by generating their own microclimate.

Animal lovers, keep an eye out for wallabies, wombats, and Tiger snakes slithering through the swampy undergrowth.

The highlight for many who venture into this true wilderness is a climb to the top of King Solomon's throne, with its sweeping view over the overland track and cradle mountain-lake St.

Clair National Park.

Treks through the alpine region have been part of Tasmania's appeal for decades, but walks along its coastline are becoming equally renowned.

This impossibly beautiful place has been called the bay of fires since Captain Furneaux, on Cook's second voyage to Australia, sighted it from the sea in 1773.

He noticed a number of fires burning along the coast and concluded the area was densely populated by aboriginal people.

Shell middens where they once feasted on seafood can still be seen in the landscape, but by and large, the place is deserted, a 30-kilometer stretch of white canvas splashed with garish colors straight out of Pablo Picasso's playbook, a masterpiece of nature, boldly pairing orange with blue.

[waves crashing] the fine white sands that create the string of beaches that form the basis of the bay of fires track owe their purity to the high quartz content in the eroding granite boulders that sit proudly on each headland.

The orange that completely covers some of these rocks is a type of lichen, a combination of algae and fungus that live together in a symbiotic relationship.

And that blue... [wave crashing] well, that's just mother nature showing off, attempting to compete with some of her own better-known efforts in the great barrier reef thousands of kilometers to the north.

She's certainly succeeded in making the color brighter here, but not the water temperature warmer.

Even in summer, it can be a bracing 16 or 17 degrees, a good 10 degrees cooler than the tropics.

The bay of fires walk provides access to another watery wilderness hidden just behind the dunes.

Stained by the tannins that leach from the native forests that line the riverbanks on either side, ansons waters are calm and inspire a moment of reflection.

Drifting through this peaceful sanctuary is a fitting way to end this short but truly great trek, which offers, in addition to the exquisite scenery, time out from everyday life, a chance to reconnect to nature without having to venture too far out of one's comfort zone.

Wildlife encounters often happen by chance on many of the world's greatest treks, but sometimes they can be the main motivation for taking a walk in the wild, the promise of coming cheek to jowl with some of the most elusive and wondrous creatures on our planet.

For many trekkers, it simply doesn't get any better than this-- a chance to see gorillas in the wild.

With only two populations of mountain gorillas left in the world, sightings such as this are a rare privilege.

The mountain gorillas that live in Rwanda, in Africa, hide out on the isolated, dormant volcanoes that dominate the virunga mountains.

It's challenging enough just to reach the entrance to the park that protects them, let alone venturing into their silent jungle realm.

The gorillas could be anywhere on the mountain, so guides use walkie-talkies to talk to experienced trackers who are deep in the jungle, searching for key family groups in advance of any trekking parties.

At one point, there were fewer than 240 gorillas living in the wild.

Now their numbers have bounced back considerably, thanks in no small part to the conservation efforts American primatologist Dian Fossey inspired and the protection the gorillas are afforded by their sanctuary.

Scientists estimate the total population here in Rwanda and neighboring Uganda to be around 900 individuals, forming dozens of tight-knit family groups spread out across the misty virungas.

Gorillas are the largest of the great apes, but often the first family members trekking parties encounter are quite small, tiny toddlers rolling around on the floor of the jungle without a care in the world.

As they get older, they get more adventurous, swinging from the overhanging bamboo, a skill that clearly takes practice.

Where there are young gorillas playing in the sunshine, the rest of the family troop won't be too far away, mothers and babies, aunts and uncles, and keeping a wary eye out for danger, the dominant male of the group, the mighty, muscular silverback.

A big male can weigh 160 kilos and stand a good meter and a half tall, but even when sitting, they're imposing.

Seeing a massive silverback at close range in the wild is one of life's truly great experiences.

But, on the other side of the globe, one of mother nature's tiniest creatures is set to leave an equally large impression-- the monarch butterfly.

Trekking into the Sierra Madre, the mother mountains of mexico, is a relatively straightforward undertaking.

And provided the butterflies are cooperating, hikers can expect to reach their destination in under an hour and a half.

It's all uphill, of course, but the vision that awaits is nothing short of a miracle-- tens of millions of monarch butterflies, resting after the first leg of their epic migration.

Fluttering up to 150 kilometers per day, this super-generation of monarchs have flown two and a half thousand kilometers from their summer breeding and feeding grounds in Canada and the U.S.

Huddled together on the branches and trunks of great stands of oyamel fir trees, this is where they'll ride out the winter.

Closing their wings to hide their color, they try to blend in with the trees to avoid being eaten by birds.

Once winter's done and dusted, the butterflies will wing their way en masse back to the north, but no individual monarch will complete the return journey on its own.

This phase of the migration is more of a group effort to ensure the perpetuation of the species, a relay where the baton for life is passed from one generation to the next.

Since each individual butterfly on the return journey will only live for four to five weeks, it can take four or five generations for the monarchs to complete their migration back to Canada.

Trekking is in so many ways an apt metaphor for life.

Sometimes you go up, sometimes you go down, and you try to take it all in stride by taking one small step at a time.

One country that has more than its fair share of spectacular ups and downs is New Zealand.

You can even walk the entire length of the country along the newly opened Te Araroa, which is Maori for the long pathway, clearly an understatement in most people's minds.

This daunting 3,000-kilometer trail stretches from Cape Reinga in the north to bluff on the southern tip of the South Island.

It's already well on its way to achieving the recognition its founders envisaged when they first conceived and then opened the trail in 2011, fast becoming the best walking trail in the world.

It takes in an incredible variety of landscapes that showcase the very best of New Zealand's vast wilderness, its exquisite forests, empty beaches, and ultimately, its breathtaking panoramas and mountain views.

The North Island section of the Te Araroa trail includes the Tongariro alpine crossing, the most popular day walk in the country.

Just shy of 20 kilometers, this part of the track passes between two volcanoes, skirting around barren craters, steaming vents, and startling emerald lakes, which owe their brilliant color to minerals leaching into the water from the thermal areas nearby.

This day walk is even more spectacular in winter but can take a little longer to complete, especially if the snow is heavy.

Trekking the entire te araroa in one go requires a great deal of planning and commitment, and at least five to six months to complete.

It's best tackled through the spring and summer months, when the daylight hours are considerably longer and the weather a little easier to predict.

That same advice holds true for adventurers looking to tackle any of the equally grand but shorter multi-day walks throughout New Zealand's expansive wilderness.

The pick of the crop includes New Zealand's nine designated great walks.

These are the trails the kiwis themselves have voted the best multi-day hikes in the country.

Three of the notable nine are located in the Southern Alps, and their popularity is as peaked as the terrain, with the celebrated milford track regularly promoted as the finest trek in the world.

12,000 people a year complete this alpine traverse, from the shores of Lake Te Anau to the dreamy, cinematic wonder that is milford sound.

In perfect weather, this trail has all the hallmarks for a perfect three to four-day trek.

It's 53 and a half kilometers long with a negligible degree of difficulty.

It starts out flat, as all good trails should, and even when it does head toward the heavens, it's via a series of switchbacks rather than a single epic stairway, zigzagging gently towards MacKinnon Pass, at 1,154 meters, the highest point on the track.

Here, a memorial pays tribute to quintin mackinnon, the explorer credited with discovering the now famous route from Te Anau through to Milford Sound.

When hikers have had their fill of what's surely the finest view from the trail, it's all downhill from MacKinnon, but only in a physical sense, for the unfolding scenery moves seamlessly from one dominated by infinite views into a more intimate realm.

The enchanting and perhaps enchanted beech forests that cloak the western side of the Alps are lush beyond belief, nourished by seven meters of rainfall a year.

This deluge also feeds the region's rivers and waterfalls, including one of the highest in the country, 580-meter Sutherland Falls.

The Milford track ends at sandfly point, and, yes, hikers should heed that as a warning, whipping out the industrial-strength deet, or rancid bacon, a deterrent the local gold miners swore by in the 1860s.

However one chooses to keep the bloodsuckers at bay, it does take the sting out of lingering a little longer in Fiordland in order to take in the misty majesty of Milford Sound.

Writer Rudyard Kipling called it the eighth wonder of the world, and few visiting the area on a sunny day would disagree.

With its soaring peaks, cascading falls, and calm waters, it is every bit the grand finale to New Zealand's grandest walk.

Mountains the world over are a beacon for adventurers seeking to walk in the wild.

The Rockies, the Appalachians, and the Swiss Alps, they all deserve recognition and attract hikers in their droves.

But the one peak that's never far from the top of any list naming and fame-ing the greatest walks in the world is Everest, the holy grail of the trail.

The highest mountain on Earth sits in the middle of the Himalayas, on the border of Tibet and Nepal.

And ever since Sir Edmund Hillary and Tenzing Norgay reached its summit in 1953, it's attracted trekkers like moths to a flame.

The best walks are always those that lead us not only to a specific destination, but to an enriched understanding of the world we live in and an enhanced sense of self.

And few do that as majestically as the 13-day trek to Mount Everest.

[plane humming] Most of the 30,000 people who trek to Everest Base Camp each year begin their journey with a 40-minute flight from Kathmandu, the capital of Nepal, to Lukla, a tiny airstrip Sir Edmund Hillary helped to build in 1964.

He had hoped to position the runway on flatter ground in the valley, but local farmers were reluctant to give up their best land, so it clings precariously to a steeply-inclined mountain spur.

The Sherpa people who live in the Solu Khumbu are traditionally pastoralists, but with the popularity of trekking in their region soaring higher each year, many have opted to trade agriculture for commerce.

Even more Sherpas now work as porters and guides, lending their support to the stream of international visitors that flow in and out of their homelands as fluidly as a tide.

For most trekkers, day one is an easy walk downhill to the Dudh Kosi river, but once the trail starts winding its way up towards the national park, the going gets a little bit tougher.

The national park, which is also a world heritage site, was created in the 1970s to safeguard the natural and cultural values of the region... The mountains and forests that define the Solukhumbu, and the traditions and beliefs that define her people.

They are devout Buddhists who share their mountainous homeland with a pantheon of gods.

Everest, or Chomolungma as it's locally known, is worshiped as the mother goddess of the universe, but Khumbila, a much smaller mountain in the range, is even more deeply revered as the patron god of the whole Khumbu region.

Rising just 5,761 meters, it's far too sacred to climb.

As the altitude increases en route to Everest, the vegetation starts to thin out.

Forests of blue Himalayan pine and silver fir give way to hardy rhododendrons and a species the local guides refer to as the walking bushes of Nepal, people carrying baskets full of fresh leaves to feed their livestock.

Most people trekking to Everest spend a day or two in Namche bazaar, acclimatizing to the steadily thinning air, which can make those unaccustomed to the altitude feel a little lightheaded.

It's as good a place as any for westerners to connect to the local culture and to local history, with one museum proudly celebrating the achievements of those Sherpas who have become world-leading mountaineers in their own right.

Namche bazaar sits at the junction of several old trading routes, so it's served as a commercial hub for centuries.

Long before western climbers started using it as a staging post for their expeditions, Tibetans and Sherpas from neighboring valleys came here on a regular basis to trade commodities such as yak cheese and butter for agricultural goods grown at lower altitudes.

The next significant place en route to Everest is Tengboche Monastery, the largest Buddhist complex in all of Solukhumbu.

The setting is utterly divine, an inspiration to pilgrims and trekkers, who are welcome to seek a blessing from the resident high-priest, or Rinpoche, or to simply sit with the monks in their prayer hall, soaking in the sanctity.

[men chanting] [instruments clanging] the terrain beyond tengboche gets more and more desolate, and the mountains, closer still, until finally, at the end of the Khumbu valley, Everest base camp comes into view.

At over 5,000 meters, the oxygen level here is half what it is at sea level, so even fit trekkers will need to climb slowly if they wish to climber higher in order to see the summit from here, following narrow tracks made by yaks up to a point where, weather permitting, the view opens to reveal the mountain, fixed like a jewel in a regal crown of peaks the Sherpas call the throne room of the gods.

Unsurpassed scenery, unbridled freedom, unforgettable encounters.

Wherever we choose to walk in the world, these simple pleasures are par for the course.

There are few forms of travel as gentle on the planet and few as satisfying to the soul.

Even when you're pushed to the limit of endurance or forced to share the view with a thousand strangers, the sense of achievement at journey's end will still be deeply personal and profound.

[people clapping]