Rome's semi-secret peephole vista is also a former Crusader stronghold.

Hundreds of lucky felines haunt the ruins where Caesar was murdered.

The crypts of Capuchin friars decorated with the bones of over 4,000 friars, including an entire "crypt of pelvises."

Thirty creepy ghosts now inhabit this decaying 14th-century church.

Massive installation of Europe's negative stereotypes.

These 17th-century mummies are no longer naturally preserved, but remain on display today.

Underneath the city that invented pilsners are a series of historic tunnels that have been storing beer for centuries.

The medieval home is still engraved with the symbol of the profession, an eye flanked by two axes.

After 400 years of being closed to the public, this monastery's underground tunnels and secret garden are now a museum.

This church is named for one of the most dramatic tales in the early Christian church.

Dynastic Home of the De Piro Family.

A centuries-old forgotten underworld lies beneath Malta.

The floor of this spectacular Baroque sanctuary is covered in memento mori.

Step aboard the first ship to circumnavigate North America.

Seemingly grown on some other world, these New Mexico rock formations look like a disused science fiction set.

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

This vertical pinnacle in China was the inspiration for the floating mountains in the movie “Avatar.”

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

Tubing through a cave lit with glowworms is a magical underground experience.

A faux desert landscape in the middle of the jungle that sprouts oases during the rainy season.

Mother Nature outdoes herself with this stunningly beautiful set of caves carved into marble.

A salty red wasteland in Tanzania is a breeding spot for endangered flamingos.

The oldest natural history museum in western Canada houses more than 5,000 vintage botanical and zoological specimens.

The strange “kaiju” of Lake Imba that allegedly killed over a dozen men with a single strike of lightning.