- [Narrator] Many of the world's most significant man-made wonders serve not as places of refuge, but as powerful signposts.

They are towering monuments that shine a guiding light to illuminate our way or imposing landmarks that warn us to take an alternative route.

But more than giving us direction, they tell us a story.

Giving physical form to an idea, they characterize powerful forces or commemorate power lost.

They can put us in touch with a long forgotten past or inspire hope for the future.

They can give voice to a people, a place, and a point in time... or they can literally place an ideal on a pedestal.

These are the world's greatest landmarks and monuments.

♪ ♪ Landmarks don't come any bigger than this.

The Great Wall of China is considered the largest construction project in human history.

Hindered by no natural barrier, it snakes its way across deserts, over mountains, to where the land meets the sea, guarding China's historical northern borders against the dreaded invasions of nomadic warriors.

But what was once intended as a barrier has become one of the Middle Kingdom's greatest attractions, drawing more than 10 million visitors a year.

(indistinct chatter) The Great Wall is not a single structure, but a series of interlinking walls, trenches, and natural barriers that sprawl in a general east-west line across northern China.

This man-made wonder collectively measures over 25,000 kilometers.

That's three times the length of the mighty Amazon, a river that cuts its way through no less than seven countries.

Threading its way through time and space, this unparalleled endeavor of engineering was undertaken by two separate dynasties over the course of 2,000 years.

Championed by Qin Shi Huang, the founder of the Qin Dynasty and first emperor of a unified China in the third century B.C., the original wall was more than a landmark, it was a monument to the unification of the country.

The newly-crowned emperor ordered the merging of smaller existing walls to create a collective bulwark against the now common enemy of barbarian nomads to the north.

It was a relentless and dangerous task.

Scholars estimate that up to 400,000 conscripted workers died during this phase of construction and believe their bodies are buried within the foundation of the structure itself.

Built using wood and rammed earth, the true extent of Emperor Qin's wall may never be known, as the majority of this section of the wall has been lost to the erosions of time.

Today, the most well known sections of wall are also the best preserved.

Located just north of Beijing, the nation's modern day capital, these sections were constructed by the powerful Ming Dynasty between the 14th and 17th centuries, more than 1,000 years after the demise of the Qin Dynasty.

These iconic stretches, with their wide-paved walkways and turreted fortifications, have proved to be not only some of the grandest, but also most robust sections of the wall.

Scholars believe that the strange meanderings of the wall were designed, in part, to harmonize the structure with its environment.

By adhering to the ancient teachings of wind and water known as feng shui, the architects hoped to employ powerful natural forces to strengthen the wall against attack... but nothing was left to chance.

♪ Running for more than 6,000 kilometers, the walls of the Ming Dynasty feature more than 25,000 watch towers.

If an enemy was spotted, beacon fires within the towers would be lit, alerting the next tower to light its signal fire and so on, relaying the message to the nearest troop garrison to send reinforcements, but as the Mongolian warlord Genghis Khan once said, "A wall is only as strong as the men who guard it."

During his lifetime, he and his infamous Mongol hoards managed to breach the wall on several occasions.

But while the Great Wall's ultimate defeat came long after the time of Genghis Khan, his word's rang true in its downfall.

In 1644, facing an invading Manchu force outside the wall and an internal rebellion within, Ming general Wu Sangui granted access to the Manchus, who had promised to help quash the rebellion.

But once inside the wall, the invaders quickly seized power, bringing an end to the Ming Dynasty and the defensive life of the wall.

Over its long course and long history, the Great Wall of China has stood for many things.

As a symbol, it unified a nation, as a fortification, it protected but also isolated what was to become known as the Middle Kingdom, and today, revered as one of the Seven New Wonders of the World, the Great Wall stands as a landmark of national pride... one that China is happy to share with the many millions of foreigners that it was originally built to repel.

♪ Paris, the French capital, is synonymous with many things, Romance, chic boutiques, revered cuisine, historic architecture, and artistic treasures.

But if this remarkable city could be distilled into one image, into one monument, it would undoubtedly be this one, the Eiffel Tower.

Today an unmistakable symbol of Paris, This structure was originally only intended to be a temporary fixture... a powerful, but ephemeral work of landscape art created to mark a momentous occasion in the final years of the 19th century.

The Eiffel Tower stands in the Champ de Mars, a grassy public park on the Left Bank of the Seine River.

130 years ago, this location was to serve as the entrance to the 1889 World's Fair, an international exhibition to showcase the nation's achievements.

And for this monumental event, the city needed a monument, one that would demonstrate France's architectural creativity and masterful engineering to the world.

Over 100 artists submitted plans for this tall order, but one stood head and shoulders above all others.

The soaring design of the Eiffel Tower promised to become the tallest man-made structure in the world, a powerful statement, indeed.

(tourists chattering) - [Announcer] Designed by the greatest engineer of his time, Gustave Eiffel.

Magician in iron, he was called.

The great tower was bold enough to be controversial.

A masterpiece of structural engineering, it remained a celebrated landmark, a symbol of World's Fairs everywhere.

- [Narrator] While the Eiffel Tower bears the name of renowned bridge builder, architect, and metals expert Gustave Eiffel, it was two engineers employed at his architectural firm, Maurice Koechlin and Emile Nouguier, who submitted the initial plans for, what is today, a universally adored monument.

But initial reactions to the project were decidedly less enthusiastic.

As construction commenced in 1887, a collective of 300 artists, writers, and architects, one for every meter of the tower's height, launched a high-profile protest to quash the ambitious project.

Deriding the tower as a useless black smokestack that would disfigure the beautiful city of Paris and humiliate its far more tasteful monuments, the group's uproar generated international headlines but did not halt construction.

♪ Eiffel and his team, undeterred by the uproar, powered on, and the tower rose from the ground at a rapid rate.

The ambitious design required 10,000 tons of iron to be held together by 2.5 million rivets.

Every component was pre-fabricated at Eiffel's Parisian factory, from the biggest beam to the smallest nuts and bolts.

Despite ongoing political opposition, the project ran relatively smoothly, and construction took just two years to complete.

In the final hours, scores of dedicated steelworkers worked through the night to ensure the towering entrance was ready for the opening of the World's Fair on the 6th of May, 1889.

Dubbed the Iron Lady, the Eiffel Tower became an instant hit... and many of its initial detractors publicly apologized for their earlier criticisms.

At 324 meters tall, it had surpassed the Washington Monument to become the world's tallest man-made structure.

A distinction the tower would maintain for 41 years until being overtaken by New York's Chrysler building in 1930.

Once a controversial and ephemeral artwork, today it's hard to imagine Paris without its iconic tower, an engineering triumph that continues to attract more visitors than any other monument in the world.

♪ By leaving an indelible impression, a landmark can define a place, pay homage to a watershed moment in history, and immortalize the lives of those that created it, but some landmarks are so old that their stories have been lost to living memory, leaving us to ponder their very existence.

Are these the remains of a ritualistic site of an ancient religion?

A calendar marking astronomical events?

Or a landing pad for alien visitors?

Stonehenge is arguably the world's best-known prehistoric landmark.

It's also the one we know the least about, but one thing is clear, it remains a cherished site that means different things to different people.

Stonehenge stands on a chalky plateau in the small county of Wiltshire in Southwest England.

Scholars believe that the origins of this prehistoric stone circle date back to between 3000 and 2000 B.C.

While the largest of Stonehenge's stones, measuring up to nine meters tall and weighing over 40 tons, were likely sourced from the surrounding region, the smaller ones, which still weigh about as much as an elephant, have been traced to a site in Wales some 300 kilometers away.

For a people that lacked the basic technology of the wheel, the effort of transporting these enormous rocks would have certainly been a Herculean task.

Even with today's scientific capabilities, archaeologists are unable to determine exactly how they did it.

- [Man] Two, three, four.

One, two, three, four.

While some speculate the stones were floated on rafts or dragged by teams of oxen, others suggest that they were rolled along an endless line of tree trunks to reach their distant destination.

But what is more intriguing than the mystery of how it was done is the question of why.

There is archeological evidence to suggest Stonehenge was used as both a ceremonial site and cemetery, but as those that used this place left behind no written record, their ways of life have been lost to history.

They remain tightly held secrets known only to the mysterious stone circle that has long outlived its creators.

It's believed that, over its 5,000-year history, Stonehenge has evolved with the times.

Frequently falling into disrepair before being repurposed to cater to the varying beliefs, rites, and rituals of the many peoples that have since come and gone.

And it continues to do so in modern times.

From hippies to new-age spiritualists and UFO researchers, there are many who feel a deep connection with this mystical site even today.

One group in particular asserts a long and illustrious relationship with these sacred stones.

- [Reporter] At 3:50 a.m.

first light and back on the job waiting with the larks for the earliest sunrise of the year, the Druids.

For the last 13 years, they've been disappointed.

The sunrise, vital to their ceremony, was obscured by rain and mist, but this year, the sun appeared on time.

- [Narrator] The Druids, an ancient Celtic religious order dating back to the 17th century, claim to have been Stonehenge's original founders.

- I believe Stonehenge belongs to us.

I believe it was built by the Druids, and we have a prior right to be here anytime and every time.

- [Narrator] While radiocarbon dating has disproved this notion, Druids to this day gather alongside more motley revelers to mark the summer solstice.

Regardless of its past, Stonehenge continues to unite people from all walks of life drawn here to marvel at the site's mysterious stories, be they sacred or profane.

But today, they must do so at arm's length.

In an effort to protect this World Heritage listed site from overuse, it was closed off to the general public in the 1990s.

As archeological research continues here and in neighboring sites, a picture is emerging of a much larger historical complex and a much larger mystery.

This ancient landmark is set to remain as one that poses more questions than answers.

♪ Even at the mature age of 130 years old, the Statue of Liberty remains the tallest statue in the United States... and a towering monument to democracy.

Situated in Upper New York Bay, the iconic statue stands upon the aptly named Liberty Island.

The Statue of Liberty was a gift from the government of France to the people of the United States to commemorate the 100th anniversary of their Declaration of Independence.

Modeled after Libertas, the Roman goddess of liberty, within her right hand she holds aloft a torch representing the guiding light of democracy.

With her left, she embraces a tablet inscribed with that most momentous of dates, the 4th of July.

The broken chains lying at her feet, a powerful symbol of emancipation.

Although free from the shackles of tyranny, the story of her coming of age is fraught with obstacles every step of the way.

The Statue of Liberty was the vision of French political thinker Edouard de Laboulaye who, in 1865, began advocating for a monument to celebrate American democracy, quietly hoping that it would spur calls for democratic reform in his own homeland.

♪ The honor of creating the statue was afforded to renowned French sculptor Frederic Auguste Bartholdi, who hoped to have it completed for the 100th anniversary of the Declaration of Independence in 1876.

Bartholdi handcrafted his work from heated copper plates using a hammer to intricately shape his masterpiece.

To add a deeply personal touch, the now famous face of the statue was modeled on his own mother's.

As he neared completion, Bartholdi became concerned that his statue may not stand up to the infamously strong winds of New York bay.

He called upon the services of innovative engineer Gustave Eiffel, who would later find recognition in a tower bearing his own name, to construct an iron skeleton within the statue.

Given the scale of the subject, it was a feat that had never been attempted.

While the French hammered out the challenges before them, architects in the United States were faced with problems of their own.

The Americans were charged with building a base for the statue.

It wasn't the design of the pedestal that was the issue, it was the cost, and plans for a solid granite base were replaced with a cheaper option, concrete.

With a base measuring nearly 20 square meters and walls over six meters thick, at the time it was the largest cement pour ever attempted, but it was ultimately successful, and the concrete mass was clad with a granite facade.

By 1886, almost a decade behind schedule, the Statue of Liberty was ready to make her month-long journey from France to New York.

Once stateside, it took over four months to re-construct the monument upon her new pedestal.

Now standing 93 meters tall, the Statue of Liberty was inaugurated by President Cleveland on October 28th, 1886.

Watching over the Bay of New York, the Statue of Liberty soon became a beacon of hope for immigrants seeking a new life in the land of opportunity.

From the late 19th century to the mid-20th, some 12 million new Americas were welcomed by Lady Liberty's assuring gaze... as they passed through the nearby immigration station on Ellis Island.

Today, upholding the highest human ideals, Lady Liberty is a stirring monument to freedom, hope, and democracy that continues to resonate around the world.

♪ This ruinous landmark is more than an iconic structure that defines the area in which it stands.

It's a historical reminder of a bygone era within which lie some sobering messages for our lives today.

♪ Rome, the capital of Italy, was once the heart of the Roman Empire, one of the greatest powers the world has ever known.

Amongst its most salient symbols of might and grandeur, the Colosseum.

Originally known as the Flavian Amphitheater, the Colosseum was built between 72 and 80 A.D., a gift to the people of Rome in the tumultuous years following the excesses of the infamous Emperor Nero.

And the gift was gratefully received.

For centuries, this was the most celebrated venue for ancient Rome's most popular entertainment, a fearsome blend of combat, theater, and cold-blooded murder.

Shaded from the hot Roman sun by huge canvas awnings, up to 80,000 spectators packed in to the Colosseum to watch public executions, gladiatorial contests, live animal hunts, and epic re-enactments of famous battles.

It's estimated that over 400,000 people, at the time, equal to the male population of Rome itself, were slaughtered within this arena during its 400 years of operation.

Whether in awe of its magnificent structure or captivated by its gruesome history, the Colosseum continues to draw a crowd today.

The ruins of this once hallowed venue receive over six million visitors a year.

This, the largest amphitheater ever constructed, was built of stone, concrete, and marble.

The distinctive exterior once contained 80 arched entrances supported by decorative columns differing in styles across the three levels.

Once a symbol of strength and endurance, the Colosseum fell into ruin with the fall of the Roman Empire in the fifth century A.D.

Over time, natural disasters, neglect, and the looting of its resources decimated the building.

It's thought that much of the foundation of St.

Peter's Basilica in Rome's Vatican City was constructed from the Colosseum's crumbling brickwork in the early 16th century.

Today, although a shell of its former self, the Colosseum remains a sobering landmark in modern Rome.

A reminder, both glorious and gory, of a time when this city was the heart of the mightiest empire the world had ever known.

♪ (dramatic music) Christ the Redeemer is the world's largest art deco statue and, for many, the ultimate religious monument.

With His arms held wide in an unending gesture of acceptance and reverence, Brazil's most famous landmark casts his serene gaze over the city of Rio de Janeiro.

♪ Christ the Redeemer stands atop Corcovado Mountain.

Portuguese for hunchback, this nearly 700-meter-high granite peak acts as a pedestal, reverently holding the statue aloft, ensuring it can be seen from just about anywhere within the city below.

Rio de Janeiro is famed as one of the most vibrant cities in the world.

(people cheering) It's fringed by mountains and luscious rainforest, but the urban landscape here can be just as wild.

With the seductive allure of its bustling beaches, Rio is also home to the biggest party on the planet, Carnival, a bubbling melting pot of cultures, colors, and creeds, all united under the open arms of Christ the Redeemer, a monument to the nation's predominant faith.

Today, Brazil plays host to the world's largest Catholic population, but following the separation of church and state in the late 19th century, some of the religion's most devoted believers feared a state of godlessness growing within their society and lobbied for the building of a statue on top of Mount Corcovado to watch over their wayward flock.

In 1923, Brazilian engineer Heitor da Silva Costa won a commission to design a statue funded almost exclusively through donations from the Catholic community.

After his initial plans were parodied and ridiculed, Silva Costa sought the aid of renowned Brazilian artist Carlos Oswald, who is credited with creating Christ's iconic pose, signifying the redemption of mankind at the crucifixion, but this powerful symbolism posed its own problems.

In order to be visible from all areas of the city, the structure not only had to be 30 meters tall, but made from a material strong enough to support the weight of its outstretched arms, which in turn, spanned more than half the width of a football field.

The solution came in the form of reinforced concrete, which at the time was considered the building material of the future, but it was not without its limitations.

While concrete offered the required strength to uphold his design, Silva Costa considered its finish unacceptably rough, far too crude for a such a graceful monument.

He needed to find a simple, but elegant solution.

In 1926, Silva Costa was inspired by French mosaics whilst working in Paris with French sculptor Paul Landowski, the creator of the statue's pensive art deco face.

It was decided that the silky smooth finish of polished soapstone would provide a luxurious luster and the statue's final design element.

♪ Four years in the planning and five years in construction, this iconic symbol of Christianity was officially revealed to the world in October 1931.

The statue is almost as wide as it is tall, and in today's money, cost the equivalent of nearly $3.5 million to create... paid for almost entirely by the dedicated Catholic residents of the city which it overlooks.

♪ Recognized as one of the New Seven Wonders of the World, the statue is a triumph of the artistic, scientific, and divine elements that brought it to life.

Christ the Redeemer has been embraced as much by the people of Rio as he symbolically embraces them.

♪ Throughout history, castles have been designed with one primary function in mind... to withstand sustained attack.

Although purpose-built for strength and endurance, over the centuries many of these once mighty bastions have fallen to either the hand of the enemy or simply the ravages of time, but not all have suffered such a fate.

Located in Japan's southwest, this is Himeji Castle, an unmistakable landmark that looms above the city that shares its name.

It's a rare example of Shogun era castle architecture ♪ and has survived the centuries thanks, not only to its imposing battlements but also its beauty.

♪ Occupying a strategically defensible hilltop above Himeji City, there have been fortified structures here in one form or another since the 14th century.

The castle as we see it today is the result of continued expansion and remodeling by a succession of samurai warlords throughout Japan's feudal Shogun era.

Partially destroyed in the early 17th century, during its reconstruction, great care was taken to not only improve the castle's fortifications, but to embellish its visual appeal.

(Woman singing in Japanese) Once completed, Himeji became known as White Heron Castle... (singing continues) owing to the building's resemblance to the elegant predatory bird.

But despite the newly introduced aesthetics, the castle remained as formidable as ever.

(speaking Japanese) Surrounded by several moats to deter invading forces and to store water in case of fire, the castle complex boasts a wealth of advanced defenses.

(speaking Japanese) Loopholes were bored into the castle walls to allow defenders to fire upon interlopers while remaining hidden and protected.

(speaking Japanese) Deeper within the complex, in an effort to slow, divide, and bewilder potential invaders, a maze-like series of gates and paths was designed to protect the castle keep, a bastion of last resort.

Several stories of Himeji's towering castle keep feature stone throwing platforms from which defenders could launch heavy objects or pour boiling water onto intruders.

Although it would have been a more effective weapon, boiling oil was ruled out as an alternative, as it would have damaged the castle's famed plasterwork, a sentiment that illustrates the Shogun's deep reverence for Himeji's aesthetics, even during times of war.

To deal with any invaders that did manage to penetrate the well-protected keep, surprise attacks could be launched from secret chambers known as warrior hiding places.

A force to be reckoned with, Himeji Castle stood as an impenetrable stronghold, if only in reputation.

As no major battles were ever fought here, to this day, the castle's impressive defenses remain unproven.

Surviving relatively unscathed for hundreds of years, this landmark wasn't truly tested until the 20th century, but it wasn't sword-wielding samurai that threatened the castle.

It was earthquakes, the Allied bombings of World War II, and perhaps most dangerous of all, the encroachment of property developers.

Ultimately, it wasn't Himeji's battlements that preserved the castle from ruin, but its historic charm and beauty.

Maintained as a testament to the intriguing Shogun era, in 1993, Himeji Castle became one of Japan's first world heritage listed landmarks... and is now one of the nation's busiest tourist destinations and most prized national treasures.

♪ Monuments are built with human knowledge and endeavor.

This one was built for them.

America's Smithsonian institution is the world's largest museum and research center... an unrivaled celebration of human achievements in art, science... and culture.

The most visible and monumental components of the Smithsonian are its 19 museums and galleries, 16 of which are found in Washington, D.C.

The capital and center of political power within the United States, Washington is, unsurprisingly, a city of monuments.

The heart of the Smithsonian resides in esteemed company alongside the National Mall.

Neighboring monuments like the Capitol Building, the hallowed shrine of the Lincoln Memorial, the Washington Monument, and the mall's 618-meter-long reflecting pool.

Founded in 1855, this building, known fondly as the castle, is the original home of the Smithsonian Institution, but it's not where its unusual story begins.

Before it became a reality, this monument was conceived in the dreams of one man.

The illegitimate child of a wealthy Englishman, James Smithson was a chemist and mineralogist who dedicated his life and, in a way, his afterlife to science.

Following his death in 1829 and the passing of his only heir a few years later, Smithson's estate, valued at nearly $11.5 million in today's currency, was decreed to be passed to the United States, as he wrote, "To found at Washington, "under the name of the Smithsonian institution, "an establishment for the increase and diffusion of knowledge."

And so it came to pass that the Smithsonian Institution was founded in 1846.

That which started out as the grand gesture of one man has since grown into the world's premier research, education, and museum complex.

Nicknamed the nation's attic, the Smithsonian Institution houses more than 150 million artifacts across 19 museums, nine research centers, and a National Zoo.

Today, this monument to knowledge welcomes around 30 million visitors every year... each of whom is granted entry free of charge in accordance with the founder's wishes.

The Smithsonian is described as a hall of fame for everything that matters.

♪ The complex stores and preserves items of significance across a wide range of disciplines, including art, science... natural history, and culture.

The institute's eclectic displays cover everything from the stovepipe hat worn by President Lincoln, to a restored model of the starship Enterprise.

In recent years, the National Air and Space Museum has been the most popular of the Smithsonian's complexes.

In fact, it has the distinction of being the most visited museum in the world, attracting over nine million people a year.

This monument pays tribute to the astounding history of human flight.

It houses the original Wright Brothers' plane and the Apollo 11 command module... craft that can be considered monuments unto themselves, encouraging young minds to reach for the stars.

Born of the dreams of a foreign national, founded with more than 100 sacks of gold, and developed into one of the greatest centers of learning and knowledge on the planet, today the Smithsonian Institution is a monument that inspires us to be proud to be human and continues to support the pursuit of scientific breakthroughs that may one day be celebrated by future generations.

♪ Scientific in construction, artful in execution, and transcendent in their legacy... the world's greatest landmarks and monuments are pages from the human story, at times celebrating what it is to be human... at others, reminding us not to repeat the mistakes of our past.

At their best, these man-made wonders open a dialogue between our past, present, and future and become all the more intriguing when that message is lost to time.

By leaving room for interpretation, for discussion, and for complexity, the world's greatest landmarks and monuments are less static structures and more living entities.

♪