An abandoned colonial French prison notorious for its hellish conditions.

An ancient instrument used to measure the waters of the Nile so Egyptian farmers would know whether to expect famine or flood.

Storied crypts fill the most famous cemetery in Colombia.

Cathedral carved out of salt, located a mile below the earth's surface.

A 10 million-ton rock once worshiped by the Tahamies Indians, accessed by an astounding staircase.

This picturesque mansion has gone from opulent ruin to nature museum.

The caldera of this mini-volcano has been turned into a naturally heated mud bath.

An explosion of natural color known as "the river that ran away from paradise."

The Natural History Museum that time forgot.

Eastern Bloc nostalgia, anybody?

"Holy Wisdom" overlooks the city that became its namesake.

Massive, unfinished broadcasting station stands as a monument to the fall of communism.

One of the largest mines in Bulgaria is now home to a vast museum more than 100 feet underground.

This ominous Albanian fortress houses tanks and downed planes as a reminder of their victories over Western imperialism.

"Unity, Creativity, Beauty."

Thousands of objects tell the story of a city famous for its tobacco.