Uncovering ruins from the past has been integral to our understanding of ancient civilizations. But sometimes, what remains of these cultures raise more questions than answers. For instance, why did once great empires such as the Maya or the thriving Khmer people at Angkor Wat suddenly vanish? And what secrets lie preserved under the ashes of the Roman city of Pompeii?
Most disappearances can be explained by either foul play or bad luck. However, there are some cases that defy conventional wisdom. How can a modern jetliner simply drop off radar screens?