The crypts of Capuchin friars decorated with the bones of over 4,000 friars, including an entire "crypt of pelvises."

Gaudí's famously flamboyant architectural style is on full display in this sprawling park and garden.

The former 1920s mansion of a prominent Catalan developer was used as the Soviet Embassy during the Spanish Civil War, and there is still a bunker below the garden.

A once-secret library of Freemason history in Catalonia.

This small museum displays a collection of outsider art and scale models of past "treatments" for mental illness.

Medieval irrigation channels built into the sides of mountains provided Valais with water for hundreds of years.

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

This hauntingly beautiful cemetery outside a medieval citadel is full of winding paths and ivy-covered graves.

This enormous abandoned prison was once dubbed the "Bastille of Romania."

A medieval church built up to defend its village.

A collection of items from a way of life that no longer exists.

This Romanian village may have been drowned, but it is long from forgotten.

The Natural History Museum that time forgot.

A muddy alien landscape that is home to rare species of exotic plants.

A giant portrait of an ancient king looms over the river.

No one knows who built this strange cave of worship or exactly why.

Conspiracy theories and occult legends surround this mysterious natural rock formation.

Some call this eerie forest of crooked trees the "Bermuda Triangle of Romania."

The possible imprisonment of Vlad the Impaler here earned the medieval castle its nickname, "Dracula's Castle."

This solitary monastery may hold the remains of Vlad the Impaler (but probably not).

A small town Romanian cemetery filled with darkly humorous gravestones.

This elaborately decorated, fairytale-like Romanian royal palace is one of the most striking castles in Europe.

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

Moss and stone turn this waterfall into an otherworldly liquid veil.