A Franco-era dam flooded (almost) everyone out of this centuries-old Aragonese town.

A museum dedicated to the Spanish occult in a town that was terrorized by the Inquisition.

A medieval village holds a very modern hotel.

A centuries-old complex of hand-dug stone chambers has sheltered locals in times of trouble.

This volcanic cave lake is essentially hard proof that Iceland is the most magical place on Earth.

This opulent hotel has been visited by Spider-Man, Charlie's Angels, and the Ghostbusters.

An odd, ancient window that may have once been part of a brutal prison is embedded in the side of New York's Police Plaza.

The maximum security facility was once thought to have "the bloodiest 47 acres in America."

A historic London pub with prison cells in the cellar and a "spy room" on the second floor.

The world's first underground farm is in a World War II bomb shelter beneath the streets of London.

A beautiful and abandoned New York subway station from 1904, complete with chandelier.

This curved Manhattan building was built to house the opulence of John D. Rockefeller's oil empire.

Wall Street has a new heroine, a bronze statue of a small but fierce girl.

The construction of a tram line unveiled hidden remnants of the old medieval city.

This ancient Roman bridge and aqueduct still stands as a wonder of classical construction.

Series of underground houses inhabited continuously for centuries.

A natural arch carved by a river gave its name to the so-called "Cave of Forgotten Dreams."

Harry Potter once visited this massive limestone cliff, which was carved by an ancient glacial river.