An alchemist's "magic door" stands in the middle of a Roman park.

Two waterfalls flow down the cliff faces decorated with rare natural basalt columns.

A Romanesque tower appears when water levels drop.

The ghost town left by the worst nuclear disaster of all time is being taken over by nature and urban explorers.

A 400-year-old mummified arm dangles from the ceiling of St. James the Greater, serving as a warning to thieves.

A saintly relic hidden in a Prague church basement.

The world's most important buildings shrunk to a tiny size.

The world's oldest known salt mine.

An Austrian house of bones filled with hundreds of intricately painted skulls.

Naturally formed rock city in Poland.

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

The personal charnel house of Anton Bruckner.

Unique house covered in a nightmarish mural of demons, ghosts and monsters.

Museum dedicated to the terror regimes of Hungary.

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

Artfully arranged bones of 5,800 Austrians.

Mummified monks and the accidentally interred, in a 17th-century crypt.

This former insane asylum now holds a pathological anatomy museum.

One of the best collections of wax anatomical models in the world.

The former private quarters and office of Dr. Sigmund Freud now hosts a museum housing the works of the founding father of psychoanalysis.

A museum of alchemy and a basement laboratory all housed in an ancient building in a Gothic tower.

Despite attempts by local police to discourage it, Beatles-inspired graffiti has been a means for artists to air grievances for decades.

A church of bones, decorated with 40,000 human skeletons.

The vast, legendary catacombs hold secrets much stranger than stacked bones.