The world's largest bioluminescent area was undiscovered by science until 2005.

Extraordinary sculpture garden created by an eccentric English poet.

Underground hospital complex constructed by slave laborers during the German occupation of the Channel Islands.

This 14th century castle withstood years of battle but is now sliding off the hills into the Danube.

A five-story homage to tea times past.

Erosion and time have created a naturally-formed water park.

A massive art collective tries a new take on Brooklyn's DIY music scene—by making it fully legal.

A 14th-century fortified keep showcases the masterpieces of an ingenious 20th-century clockmaker.

Scotland's oldest medieval bridge is also among the last reminders of early medieval Aberdeen.

The Devil’s own choice when he needs a drink in Brussels.

A seven-century-old jail tells a not-so-pleasant history of crime and punishment.

Gorgeous cave resemble a winter wonderland.

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

A gravity-defying "devil's bridge" that has a surprising architectural feature for its stability.

A former ironworks that was the first UNESCO industrial site.

Dilapidated ruins that once treated a notorious young serial killer, currently hosting vandals, squatters, and ghost hunters.

Museum celebrating the ocean, with the largest wunderkammer dedicated to sea exploration.

A 14th century bridge built as a fortress, where the devil lurks on one of its towers.

A community of artists and entrepreneurs seeks a simpler life on London's waterways.

A vast city of the dead, where the deceased outnumber the living by more than a million.

The bones of an old zoo crumbling in the shadow of a new one.

The "Prussian Versailles" that is as glorious today as when it was built.

Padlocks cover this rickety footbridge with love.

Island where motor vehicles are banned -- home to the only carless highway in the United States.