One of the most exquisite Lycian hilltop citadels in Turkey.

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

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

An ancient city hidden in the heart of the Sierra Nevada mountains.

Former drug lord’s manor, now a theme park. Watch out for the hippos.

This whimsical home made entirely from clay is basically a giant piece of pottery.

This Japanese-inspired labyrinth of hot springs is hidden in a Chilean forest.

A unique arch graces the Dolores River Canyon near the Hanging Flume.

A coal fire has been burning underground here since 1896.

Toss a Frisbee through the ruins of this Colorado gold mining town.

A roadside attraction filled with an astounding array of gloriously wacky vehicles.

Unlike most arches, this geological oddity formed in a volcanic dike.

The remains of an early 1900s dude ranch that operated until the 1970s.

Climb to the top of this spiritual tower, and you'll be rewarded with spectacular views.

These decaying bridges 1,000 feet high are a reminder of the skill it took to cross the Colorado Rockies by rail.

A mental health hospital dating back more than 139 years, now features a museum.

A fake mine that was made using real mining techniques which is also used as a community center.

In the middle of a suburban Denver neighborhood is a cave that once provided solace for a prominent Ute chief and his family.

Metal water storage tank turned ethereal concert hall.

A futuristic hovertrain is parked unceremoniously alongside a nondescript road.

The remains of the dam that unleashed a 15-foot wall of water on Denver.

The wreckage of a World War II bomber is hidden high in the Colorado wilderness.

Colorado's only true geyser is hidden within the San Juan National Forest.

The world's largest key collection features keys to the White House, Frankenstein's castle, and Hitler's bunker.