Barcelona's historic 19th-century sewers, whose foundations were laid in medieval times, are open to the public for exploring.

One of Antoni Gaudí's most classic buildings is well-known for its "dragon-back" design.

A temple to modernity, tucked away amid Barcelona's more well known museums.

The oldest giants in Catalonia are now displayed in a 14th-century Gothic church.

An Australian lake whose pink hue defies scientific explanation.

The world's "leaniest" tower encourages you to test the gravity of its situation.

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

Romania's only crater lake with water as pure as if distilled.

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

Gigantic Romanian salt mines used to heal respiratory conditions.

Even drowned in an ocean of toxic waste, the remnants of this Romanian village stand tall.

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

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

The Natural History Museum that time forgot.

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

A small town Romanian cemetery filled with darkly humorous gravestones.

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

This floating cinema brings new meaning to the phrase "going out" to the movies.

The hallucinogenic center of the ancient world.

Fall down the rabbit hole into a surreal journey of human consciousness "from ass to soul."