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

At this Denver landmark, the meals are compulsory, the sopapillas are complimentary, and the insanity is everywhere.

Abandoned city hidden from the world by tropical forest and isolation on the coast of Kenya.

An architect transformed this abandoned cement factory into his castle-like workshop.

Mysterious Spanish catacombs of unknown origins.

One of the world's steepest streets seems to have houses sliding down it.

The unique building practices of the Batammariba reflect the community's deep reverence for and connection to the earth.

What was once believed to be a church floor turned out to be the artwork of geology.

This Quebec estate is home to the elaborate gardens of a self-taught horticulturist.

This railroad track was so secretive that it was omitted from all maps.

Outside of one of Britain's most renowned social clubs, a step installed specifically for the Duke.

Built to transport German U-boats through the never-completed Masurian Canal, the locks near this Polish village are now home to a rope course.

A former Canadian Pacific Railway station turned liquor store, the first and only station in Canada visited by British royalty.

A performance hall at the American Jewish University moonlights as a sci-fi film location set.

The eccentric mansion of one the most popular horror authors of modern times.

The ruins of a 19th-century aqueduct run through this Brazilian island's deep forest.

A mysterious concrete hand reaches out from between the stones of Uniwersytecki bridge.

A medieval setting reimagined into a unique art alley.

Not far from a popular beach, an unfinished, abandoned mansion for Bulgaria's last communist dictator.

A peculiar family mausoleum built by a German nobleman captivated by the occult.

This unique structure allowed boats to bypass underwater mine barriers in the channel to enter the harbor.

Built in 1870 at the bridge that connected Buda and Pest, this spectacular incline railway was almost lost forever during World War II.

The unusual patterns in this rock formation result from two distinct modes of weathering.

Remains of an abandoned coral city.