With 500-year-old secrets hidden in skeletons and stone, Machu Picchu is one of the most puzzling archaeological sites on earth. It's among the ancient world's most enduring riddles: Who built this astonishing complex, and why?

On February 24, 1942, less than three months after the Japanese bombed Pearl Harbor, military radar picks up what appears to be enemy aircraft over Los Angeles. Air raid sirens send citizens scrambling, as troops fire more than 1400 rounds of anti-aircraft artillery at the illusive targets. When the smoke clears, the incident is veiled in secrecy and lies. What exactly triggered the

A perfectly masterminded plot leads to one of the most brazen prison breaks in American history. With only a handful of clues left behind, the search for the infamous Alcatraz escapees continues to this day. But is it really possible they survived -- and if so, where did they go?

It's a mystery from the golden age of piracy. In 1698, Captain William Kidd raids a ship on the high seas and seizes its vast treasure... but Kidd is hanged before revealing where he stashed the loot. What happened to Captain Kidd's lost booty... and where is it now?

The haunting image of the Shroud of Turin has captivated millions around the world; scientists and theologians are trying to figure out if the Shroud of Turin truly is an image of Jesus or something very different.

A look at what happened to the secret hoard of the Knights Templar, a treasure of gold, silver, gems and religious relics protected by a medieval religious order.

Most people know it as the biblical birthplace of man -- the Garden of Eden; investigating if the Garden of Eden was just a story to explain human creation or if it was a real place.

An Aztec king's glittering treasure vanishes into thin air, inspiring a 500-year search that spans continents; one of the greatest warriors of all-time amassed a vast horde believed to be worth more than $3 billion today.