European castle ruins in an American state park are actually the product of death and grief.

A series of caves, tunnels, and wells filled with fascinating figures and symbols.

A network of underground water channels that dates back to the Middle Ages.

At this ancient settlement at the foot of Mount Babadağ, honeycomb tombs are carved into a round cliff.

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

The only residents of this abandoned housing development full of identical castles are stray cats and dogs.

An Aztec snake god has taken the material form of an apartment complex.

An antique store houses the last operational diner from the defunct department store chain.

At 22 feet tall, these Bronze Age monoliths are some of the tallest standing stones in the United Kingdom.

This ramshackle ghost town is comprised of mining-era buildings collected from around the region.

Abandoned businesses, homes, and rusted cars are all that remains of this stopover town.

Designed as a labyrinth, this subterranean prison was crafted without bars or doors.

Legend says this sacred tree was a gift from goddess Athena.

An aluminum skeleton brings Chinese mythology to the French shore.

Though an earthquake destroyed this village in 1980, one former resident still walks its streets every day.

In the middle of a busy residential neighborhood, a small roofless church being reclaimed by nature.

An abandoned observatory in the middle of the Illinois prairie.

This Roman underground canal was the longest tunnel ever built until the late 19th-century.

British troops and Prohibition couldn’t stop this spot from becoming one of the United States' oldest continuously-run taverns.

This enormous sinkhole hides a secret world created from divine wrath.

One of the oldest active carousels in the country—but it might be missed by all but the keenest-eyed boardwalk strollers.

Inside this McDonald's you can dine on your Big Mac and fries next to a 2,500-year-old Roman wall.

Once part of a dam servicing an early 19th century grist mill, the tucked-way falls are a tricky-to-find urban oasis.

The Roman Emperor's lost summer home and grotto full of enormous sculptures sit along the Italian seashore.