Nan Madol is a massive megalithic city built on one of the smallest and most isolated islands in the Pacific. Millions of tons of basalt—along with monumental walls, platforms, and canals—rise up where one would expect, at most, small fishing villages. But where, then, was the population capable of building all this? Where were the cities, the countryside, the ports, and the rest of the territory?

The accounts of Atlantis by Plato and Herodotus were likely not entirely fabricated stories. We now know that—at least from a geographical standpoint—that island did indeed exist, precisely during the timeframe indicated in the stories: 11,500 years ago.

Göbekli Tepe is one of the most mysterious archaeological sites in the world. Who built its stone circles, why were they buried, and how many other sites like it may still remain hidden underground?

At 3,700 meters in the Andes stand some of the most extraordinary stone walls in the ancient world. How were they built, and why does their design make sense from above?

Fourteen thousand years ago, the world looked very different. Rising seas submerged vast inhabited regions. How much of our past may have disappeared beneath the water?