A panel of experts answered your questions on the origins and development of the twin towers; their urban, economic, architectural and symbolic significance; the creation of a postwar economic order based on global trade; and New York's role at the center of commerce, globalization, and a new kind of multi-cultural society, in this online forum.

The forum was live from September 9 through 12, 2003, and is now over. The questions and replies are posted here permanently for you to read.

Read questions and answers:

• Day 1
• Day 2
• Day 3
• Day 4

Forum participants:

• Ric Burns (filmmaker)
• Niall Ferguson (historian)
• Mike Wallace (historian)
• Carol Willis (director, the Skyscraper Museum)