One of the most easily accessible examples of the rare 1960s UFO houses.

Go surfing on this urban wave, "hacked" by local surfers.

One of Antoni Gaudí’s earliest buildings, built between 1886 and 1890 for the industrialist Eusebi Güell.

The largest Art Nouveau complex in the world is a Barcelona hospital with a 600-year-long history.

Step inside the first house designed by Catalan architect Antoni Gaudí, considered to be one of the first Art Nouveau buildings.

A beautiful but toxic fountain of mercury.

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

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

Started as a kitchen garden, now the second largest botanical garden in the world.

A museum dedicated to the history of a terrifying secret police is now held in their former headquarters.

The most visited, and possibly most controversial, museum in Germany.

The site of the famous Nazi book burning campaign of 1933 remembers its "Night of Shame".

From toys to kettles to scientific instruments, this German museum celebrates the beauty of 20th century design.

A memorial in the Tiergarten is a reminder of the suffering inflicted on homosexuals by the Nazi regime.

Berlin's old airport.

Legends say this red sandstone monolith and the dozens of smaller boulders that surround it were once a coven of witches—before a Scottish wizard turned them all to stone.

A series of idealized caves carved to entertain guests.

Stonehenge has nothing on Castlerigg’s views.

This unusual sculpture is sometimes partially, sometimes fully, submerged.

A 2,000-ton rock resting in a state of a delicate balance.

The first museum in the United Kingdom dedicated to this woodwind instrument.

This gorgeous space is England's largest independent library outside of London.

This century-old grotesque has a mysterious history and may not actually be a rabbit.

The nearly 200-year-old folly has a secret spiral staircase hidden in one of its pillars.