Christ's blood allegedly preserved in a Belgian town.

A network of concealed passageways lies within a busy London Underground station.

This macabre masterpiece of a mural is one of Francisco Goya's "Black Paintings."

One man has carved a number of natural New Mexico caves into psychedelic sandstone temples.

Gladiators battle and chariots race daily in the ruins of a once-great Roman city.

Mosaics, storks, and brothels—this ancient city has it all.

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

Huge stone depressions which may have acted as an Incan agricultural experiment.

The largest self-built castle in the U.S., six decades in the making.

This Colorado gallery is primarily for cars, but its collection also includes quilts, pottery, and more.

The footprint of a frustrated devil in Munich's Cathedral.

Part shoe store, part sociopolitical art gallery, part zoo.

One of the world's few mounted blue whales, its jaws are hinged open allowing visitors to descend into a lounge.

The once great capital of Egypt now crumbles forward as evocative ruins.

An ancient city exhumed from the depths of the ocean.

Overlooking the harbor is a beautiful neglected mansion guarded by two Egyptian sphinxes.

Is there such thing as too many fruit bats? Not anymore.

This Roman quarry once held secret masses and smuggler's contraband and is now home to rare species of bats.

These flying foxes dangle from the trees around the library like fuzzy black fruit.

Each summer, the migratory bats living beneath the bypass form "batnadoes" at dusk.

A kindergarten shaped like a cat with a tail that's a slide.

The perfectly named cave drop is the deepest in the continental United States, almost matching the height of Seattle’s Space Needle.

Hidden in the hills of Western Pennsylvania lies one of the best-kept ghost towns in America that you can legally visit.

Greenery cloaks this serene sculpture inspired by the famous Lost Gardens of Heligan.