Traditional 11th-century outdoor tannery.

Thousands of narrow alleyways in an ancient medieval city make up what's believed to be the world's largest car-free urban zone.

The other side is actually green.

One of Catholicism's four major basilicas has a series of papal portraits that are said to predict the end of the world.

2300-year-old Roman road connecting the empire.

The yawning maw of this pagan visage is said to bite off the hands of liars.

Rome’s legendary peephole vista is also a former Crusader stronghold.

The last moments of the ill-fated Pompeiians, frozen forever in plaster.

These medieval skyscrapers dominate the skyline of this small Tuscan town.

One incredible room in the Santa Barbara Courthouse is covered in wall-to-wall canvas murals.

A natural formation that resembles a camel resting in the New Mexico desert.

A small metropolis of Pueblo cave dwellings have been carved right into the hillside of this national monument.

A multi-storied adobe complex has been inhabited for more than a thousand years.

These aggressively sustainable art homes look like something out of 1970's science fiction.

A phenomenal assembly of pueblos in New Mexico is the most complete example of ancient ruins north of the border.

An immersive environment that is part haunted house, part choose-your-own-adventure, and part jungle gym.

This small piece of railroad history sits behind the parking lot of a chain grocery store.

This 19th century jail was mainly used to incarcerate the drunk and disorderly.

Air Force Academy Chapel made of 100 identical tetrahedrons works to inspire those of all religions.

This razorback ridgeline has doubled as a scenic drive since the early 1900s.

The final resting place of American icon Buffalo Bill, and a museum that aids in telling his tale.

This spectacular track has run continuously since 1882.

The Denver airport is guarded by a 32-foot-tall sculpture of a demonic horse.

When ecosystems collide in the arid Southwest.