Perhaps no land journey in human history is more famous than Marco Polo's legendary 24 year trek across Asia. But was it all just a big lie? As described in his 1299 book, the peripatetic Venetian merchant encountered such wonders as the "singing sand dunes" of Dunhuang, China, "mountains of salt" in present-day Afghanistan, and the glories of the Mongol court of Kublai Khan. Generations of Europeans were spellbound by Polo's account, yet in recent years some scholars have questioned its authenticity. For an extensive three part series in National Geographic, legendary photographer Michael Yamashita tested the famed Venetian's reputation - using Polo's own book as his travel guide.