One of the world's steepest streets seems to have houses sliding down it.

This strange geological landscape erupts with sudden bursts of water.

A battle between nature and architecture in the Cambodian jungle.

5,000 skulls in memorial to those killed by the Khmer Rouge.

Khmer Rouge's high security prison.

Breathtaking and huge 430 year old maps of Italy.

Hidden beneath the famous St. Peter's Basilica is a veritable city of the dead that may hold the remains of St. Peter himself.

This ritzy Italian market is built around a statue of an unforgiven heretic who was burned for his belief in an endless universe.

Every inch of this chapel is covered in craftsmanship from across the world.

Italian cave with exceptional acoustics and an unsavory history.

The world's most active stratovolcano is almost always erupting.

The ancient latrines of the Greeks, in all their public glory.

A marvel of Byzantine engineering under the streets of Istanbul.

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

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

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

An Ethiopian "Jerusalem" featuring a church hewn out of a single rock.

An ancient Ethiopian cave church is endangered by the simple building of a road.

A town trapped in time - 1958 to be exact.

"We Seceded Where Others Failed."

Once called Winthrop Park in 1889, home to a decidedly sexy tribute to the Monitor vs. Merrimac battle.

Once a ferry dock, radio transmitter, and now a new Greenpoint park.

Walk into the 19th century without leaving Brooklyn.