The walls and ceiling of this Polish church are decorated with thousands of skulls, with another 21,000 skeletons just below.

A fairytale Gothic castle steeped in Nazi treasure conspiracy theories.

A mysterious structure left behind on the Polish mountainside, sometimes called "Hitler's Stonehenge".

Ancient structures used to make and preserve ice in the deserts of Persia.

The likeness of the Baltimore music icon was unveiled in time for the anniversary of his Senate hearings on music censorship.

A labor of love built by local hang-gliding enthusiasts, this ideal launch spot was outlawed by the authorities and has since been largely abandoned.

After hundreds of years of settlement, this once-bustling fishing village sunk into the Chesapeake Bay.

This abandoned sea fort has become an accidental bird sanctuary.

Ship skeletons haunt Baltimore's waterways.

The oldest hall in Iceland was written of in the Sagas and features a centuries-old escape tunnel.

This fantastical waterfall is hidden in a cave located in a cracked cliff.

A modern Nordic Pompeii on the Icelandic island of Heimaey.

The oldest (maybe) swimming pool in Iceland is a stunning oasis built into the side of a lush hill.

Icelandic folklore says this giant boulder was ripped from the mountains and placed at its current location, where it became home to elves.

Three columns of volcanic rock shoot out of the ocean.

This wrecked airplane has been sitting on a black sand beach since the 1970s.

A place for ship-lovers to watch the passage of freighters traversing the Great Lakes while learning about their history.

This unacceptably tall building was the real reason for Washington, D.C.'s skyscraper ban.

The discovery site of the "Capitalsaurus," the official dinosaur of Washington, D.C.

Ruins of the elaborate house where the enigmatic costume designer threw glamorous parties for New York's theatrical elite.

A perfect replica of the beloved show's first set.

A plaque marks the underground site of one of London's "lost rivers."

A piece of outsider public art accompanied by a strange urban legend.

This stunning Connecticut mansion is actually just a one-room-deep hoax.