Hidden behind a wall for decades, this masonic lodge was only rediscovered during renovations.

Bermuda triangle lighthouse, site of mysterious disappearances, left to crumble into the Atlantic.

A subterranean Holocaust refuge within one of the world's longest cave systems.

A station built to repel pirates now attracts wealthy vacationers.

A small island less than half a mile from Venice is a forbidden island with a dark and twisted past.

A curated museum of wooden sculptures inhabits this Russian home.

A man-made island fort that has housed soldiers, scientists, and ravers.

Nightmarish example of the unintended consequences of weapons testing.

Man-made mineral caves house massive bat colony.

Immortal combat in a Moscow museum.

Back in the tiny USSR.

One of the world's largest ice festivals dazzles visitors for over a month with radiant sculptures and carvings.

Site of the largest impact event to occur over land in Earth's recorded history.

Once an opulent Art Nouveau hotspot, the Constanța Casino is one of Romania's most beautiful abandoned buildings.

A secretive collection featuring objects that were designed specifically for U.S. intelligence operations.

Since 1874, this macabre collection has developed into a museum devoted to Scotland Yard's mementos of dastardly deeds.

The industrial monstrosity known as Bagger 258 is a colossal mining machine built in the DDR - but now left for dead in a German field.

Lithuania's outdoor sculpture trail of wooden folk art.

A long abandoned hospital building on the outskirts of NYC.

This museum gives tribute to the underappreciated "Down-South Submarine."

The largest medical and anatomical collection in France lies hidden from the public.

The once forbidden "secret cabinet" of erotic art from excavations of Pompeii and Herculaneum.

An abandoned meat mecca now serves as an excellent locale for urban exploration.

This beautiful natural train tunnel is said to grant the wishes of visiting lovebirds.