Three columns of volcanic rock shoot out of the ocean.

The unique waterfall in Iceland's south features a backdrop of geometric black lava columns.

In upstate New York, gorgeous waterfalls and a watermill are slowly being reclaimed by nature.

Some of the clearest water anywhere in the world.

Highly spherical boulders on the shores of New Zealand.

Known for the tunnel that leads visitors to the water.

Thousands of well-dressed mummies below a monastery.

Europe's second largest ossuary wasn't discovered until 2001.

A toxic ghost town sitting atop a massive coal fire.

Beijing's expansive subterranean hiding spot now crumbles away as a tourist destination.

Ancient rock-hewn town that witnessed key events of Georgian history.

Forgotten German bunkers in China create a sharp cultural contrast.

These medieval tunnels provided water to the city above through centuries of civil war and plague.

Deadliest lake in the world suffocated over 1,746 people in one night.

The legendary cliffside castle of three-time Voivode of Wallachia, Vlad the Impaler.

Where Aleister Crowley taught magick in "La Chambre Des Cauchemars," his "Chamber of Nightmares."

This Nazi-built amphitheater was constructed on a sacred mountain site used by various German cults.

The headquarters of the famous Yale society.

Natural time capsule containing an alien ecosystem.

A small island less than half a mile from Venice is a forbidden island with a dark and twisted past.

The oldest of Venice's plague quarantine stations, designed to keep the medieval city safe from disease.

An island in the middle of a lake, in the middle of a volcano, in the middle of a bigger lake, in the middle of a bigger island, in an archipelago, in the Pacific Ocean.

The ruins of a lighthouse on the island Amelia Earhart never reached.

Amelia Earhart's possible place of death.