For centuries, Europeans heard legends of a mythical city in the heart of the Sahara, the source of endless caravans of gold, but it took 500 years to find.
The Confederate Army, in an attempt to turn the tide of the Civil War, launched a new and daring weapon--a forty-foot submarine. The H.L. Hunley, armed with a primitive torpedo, destroyed a mighty Union warship, yet its crew never made it home.
500 years before the Inca, a band of warriors called the Chachapoya built the greatest stone monument in the Americas. It's three times the size of Egypt's largest pyramid, yet they disappeared without a trace.