These secretive tunnels were once the site of a Royal Air Force fuel reserve depot.

The remains of 40,000 humans, meticulously stacked in a tiny churchyard shed.

What was once a bustling mining installation is now a bustling hub of contemporary art.

No shoes allowed on this trail, which is designed to be experienced barefoot.

An abandoned village that resides along the mountains of the Aosta Valley.

This stunning waterfall is the backdrop to a site that has seen continuous human habitation for 250,000 years.

Sitting atop a rock on Michamvi Pingwe beach, this restaurant becomes its own island at high tide.

This sacred, circular cave is lined with pools so clear and still that it's hard to tell where the water begins.

A salty red wasteland in Tanzania is a breeding spot for endangered flamingos.

This rare volcano spews the strangest and (literally) coolest lava in the world.

This Luxembourg cave is covered in cryptic looking marks left by mining activity.

This noble mash-up in eastern Luxembourg is part Medieval, part Renaissance, all castle.

This former Nazi castle was built as a school to train what would have been the future of the Third Reich.

Nestled in the woods lies this land art project: a hybrid between park, maze and natural monument.

This former hydraulic laboratory is now a woodland dotted with old engineering models.

This disused VLF radio station is no longer in service but the surrounding town still bears its name.

An amusement park on the grounds of an unused nuclear power plant, with a swing ride inside the cooling tower.

Between Neo-Pagans and Neo-Nazis, these strange rock formations have a curious cult following and a very strange history.

This gateway to subterranean Hanover plays jazz, pop and rock to surprised passersby.

This medieval castle overlooking the Elzbach river looks just like it did hundreds of years ago.

Germany's longest suspension rope bridge.

This Cold War–era fallout shelter was actually a storage facility for the nation's emergency currency.

Wooden pathways run through this rocky landscape, which legend says was created when a dwarven king pulled down his own castle to stop raiding giants.

Tucked away in a small German apartment is an eclectic museum devoted to West African vodun culture.