Ukrainian defense contractor's center for studying "pyramid energy."

This massive underground salt mine now holds a sci-fi theme park in its depths.

A small town Romanian cemetery filled with darkly humorous gravestones.

A 20th-century picture show in 3-D.

Countless stories attempt to explain Poland's mysterious J-shaped trees.

An underground city of salt.

Boats must transform into railroad cars to navigate this Polish canal.

An old hill fort covered in over 100,000 crosses is a symbol of Lithuanian nationalism and beliefs.

Sitting beneath an unremarkable residential building is a museum devoted to classic Pinball.

Budapest's Communist-era statues, banished to the suburbs.

Mysterious craters may have been home to an ancient cult.

Two monstrous faces loom over a village in Czechia.

Where the leftovers of love affairs can live on forever.

Where the lovelorn find a home for their sentimental keepsakes.

Space-age monument to an early 20th-century uprising.

An abandoned saucer-shaped monument in the Bulgarian mountains.

Croatia's towering concrete blossom grows from the site of a World War II concentration camp.

This stunning, out-of-the-way Croatian monument commemorates a community's uprising against occupying fascist forces.

An abandoned brutalist monument whose history has been lost to the ages.

150-year-old satirical tableaus made from stuffed frogs.

Museum of science fiction, utopias, and extraordinary journeys of the mind.

Extensive private collection of authentic Medieval devices used for human torture and execution.

Artworks by loners, prisoners and the criminally insane.

A nearly 500-year-old sculpture depicts a man eating a sack of babies, and no one is sure why.