The ancient abodes are a testament to human ingenuity amid harsh climates.

Climb a steep hill in 90 seconds on the second-oldest urban subway in the world.

A charming beach town in Turkey captures all the colors of the rainbow.

A sixth-century Byzantine cistern hidden below a modern carpet store.

Standing proud atop a Turkish bluff, this Ottoman palace has retained its grandeur despite being abandoned for centuries.

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

This remarkably well-preserved Egyptian plinth is pretty well traveled for a giant piece of stone.

Once described as the "Eagle's Nest," this ruined ancient city rests on a remote mountaintop.

A small etching on the white marble parapet was written in runic script by a Viking mercenary.

Roman ruins top white travertine terraces formed by ancient hot springs.

A marvel of Byzantine engineering under the streets of Istanbul.

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

The notorious "Hanoi Hilton" where Vietnamese colonial subjects and later American POWs, including John McCain, were imprisoned.

Ho Chi Minh's perfectly preserved body has been on display here since 1975.

The largest mosque in Cambodia was built to unite the country's Muslim community but soon sparked division and controversy instead.

A secluded, little-known temple hidden amid the dense jungle.

Khmer Rouge's high security prison.

The capital of Cambodia is named after the hill on which this ancient temple complex stands.

A battle between nature and architecture in the Cambodian jungle.

More than 100 Hindu temples are slowly being swallowed by the forest.

Within the Dadès Gorge, amazing vistas and towering cliff faces can be seen at each new curve and bend in the road.

This stucco building in North Africa was the first American-owned property on foreign soil.

Traditional 11th-century outdoor tannery.

The other side is actually green.