The best-preserved ancient theater in the world.

This Turkish cave boasts some rather bizarre associations with the King of Mount Olympus.

While not Turkey's deepest underground city, this subterranean redoubt is the largest.

Flames have been burning within this mountain for more than 2,500 years.

The deepest underground city in Turkey was designed to protect 20,000 people behind massive stone doors.

Naturally protected city carved from a rock face.

A Turkish ghost town abandoned in a population exchange with Greece.

An abused and forgotten metropolis, abandoned for centuries.

A deadly ancient portal to the underworld.

This hunter-gatherer architecture is believed to be the oldest religious complex known.

A Lycian city of the dead carved into the hillside of Southern Turkey, complete with startlingly human touches.

These tombs were built into the side of a mountain so that ancient angels could reach the dead.

In this historic region, homes and churches are carved into ancient volcanic rock formations.

Thousands of volcanic rocks carved 1,000 years ago.

Mysterious "dots" seen from a satellite in southeast Peru.

These overlooked ruins give an intimate look at the Inca Empire's urban planning prowess.

The Incas turned this ancient Wari aqueduct into an imposing defensive gate.

This set of mysterious petroglyphs in the Peruvian jungle could shed light on centuries-old activities in the region.

Ancient Peruvian fertility temple or modern money-making hoax? Either way these monoliths still look like penises.

An Inca spa, military outpost or maybe… both?

The depictions of slaughter are surprisingly detailed at this mysterious ancient site.

An abandoned Incan construction project left behind a mysterious "doorway."

This geometric feat is a testament to the Incas' mesmerizing architectural abilities.

A paradisical gorge with rapids, waterfalls, and wildlife whose raw beauty is the stuff of CGI movies.