An early work of the architect Álvaro Siza Vieira, these swimming pools blend into the beach.

An eccentric aristocrat brought these Australian natives to their current Scottish home.

A deer-headed statue that brings together a 12th-century legend and big wave surfing.

This astonishingly geometric cave has inspired everyone from Jules Verne to Pink Floyd.

Britain's only herd of free-ranging reindeer.

A nuclear bunker built to shelter the politicians and important people of Scotland in case of nuclear attack.

Built to hold the worst of the worst of the Nazi war prisoners.

This enchanting hill is home to fairy lore and a sinister local mystery.

A local tree surgeon has created a whimsical walk full of carved tree stumps near Scotland's Loch Lomond.

This futuristic German spa allows visitors to float in a pool of salt water while zoning out to underwater techno.

A tour of underground Berlin takes you through WWII air raid shelters and tunnels used to smuggle people out of East Germany.

A walkable map of the world, made from soil and stone by one man.

Six beautiful wooden giants are hidden around Copenhagen.

A 19th-century subterranean reservoir repurposed as a contemporary art cave.

The library's graceful rotunda is like a bibliophile's temple.

Sweden's first nuclear reactor, R1, can be visited 25 meters underground.

Stockholm's decidedly unique public transit system has doubled as the world's longest art gallery for decades.

The feral felines of Roosevelt Island have a small army of allies and an abandoned hospital all to themselves.

During the 1990's nearly all of the world's LSD is thought to have come from the operators of the lab once located in this missile silo.

The colorful stairs are made with marble from the world's major quarries.

An American ghost town hides along a side street in Scotland's capital.

These wooden pipes were crucial to providing water to Medieval Edinburgh.

This modern work of art was a refreshing addition to one of the oldest theatres in the city.

This grubby wall is said to be one of the Earth's esoteric energy centers.