Marco Polo became a legend after his epic, 24 year trek across Asia. Was he the world's greatest overland explorer? Or the biggest liar? National Geographic's own legend, Michael Yamashita, used Polo's book as a guide to find the truth.

Marco Polo: The China Mystery Revealed

Great Wall. 4000 miles. 1800 years. Greatest feat of civil engineering. For one year, Nat Geo photographer Michael Yamashita shot the entire Wall and the people who live in its shadow. See why this immense human feat may never be surpassed