A steampunk-styled three-floor factory churning out art, activism, and electronic beats.

Underneath this small church are 15,000 bones, arranged by an obsessive academic.

Walk through Czech history in Prague's largest graveyard.

Countless grotesque faces stare out from this eerie Prague art wall.

A Jenga-style cylindrical tower of books that appears to go on forever.

The hidden lair of an alchemist rediscovered in a 2002 flood.

Two stunning 17th-century libraries and a cabinet of curiosities.

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

The history of occult science is turned into a creepshow at this lurid Prague tourist attraction.

This unique building in the main square stands out among the city's typically Baroque architecture.

The ruins of a megalithic monument sit right in the garden of a luxurious Maltese resort.

A centuries-old forgotten underworld lies beneath Malta.

Overshadowed by other, more famous Maltese catacombs, this ancient burial chamber has one of the best examples of a ritual agape table.

These lesser-known Maltese catacombs date back over 1,700 years.

A hidden tunnel of bones in one of Malta's oldest churches.

This spectacular dome managed to survive after being bombed in World War II, in an event known as the "Miracle of Mosta."

This prison on the Maltese island of Gozo is almost 500 years old, and they have the graffiti to prove it.

Burial grounds for more than 1,000 bodies deep under the modern town of Rabat.

This subterranean necropolis holds three floors of antler-dug grave caves.

This Stone Age solar temple aligns with the sun on each equinox and solstice.

An abandoned set from the 1980 film "Popeye," claimed and repurposed as a theme park by creative locals.

An important landmark in the history of algebraic logic.

This natural sea arch highlights Ireland's rugged coastal beauty.

This 14th century tower house was once the home of Irish poet W.B. Yeats.