Once described as the "Eagle's Nest," this ruined ancient city rests on a remote mountaintop.

Rock-hewn monastery complex with hundreds of cave structures tucked away into the mountainside.

Eat like a bird in a bamboo nest.

Built over an abandoned train yard, this hidden gem is full of winding paths and offers gorgeous views of Sydney Harbour.

A castle hand-built by a Spanish dreamer in the Australian tropical jungle.

The world's largest drain sits below the city of Kasukabe, Japan.

Swiss vineyards in a UNESCO heritage site.

This amazing pedestrian suspension bridge in the Swiss Alps would give Indiana Jones nightmares.

This 170-year-old Swiss guesthouse built into the side of a mountain is best accessed by a cable car.

The steel cable lets adventurers zoom between two mountain towns at speeds of up to 75 miles per hour.

Machismo turned on its head: the lady's hand goes to the dude with the bigger brain.

Men in rubber-soled boots serve as your "brakes" on this toboggan ride Hemingway described as "exhilarating."

This abandoned five-star hotel is now a five-star urban exploration destination.

A 16th century chapel decorated with bones, skulls, and entire bodies hanging from the wall.

The oldest amusement park in the world has been providing a nice spot to have some fun since the 1500s.

Order “Proletariat’s Cutlet” at this communist-themed restaurant allegedly once visited by Lenin.

The world’s narrowest house makes for an awkward, four-foot-wide living space.

Rent out a glass igloo to watch the Northern Lights like you live in the future.

Despite centuries of architectural innovation, this French castle is being built like it's the 13th century.

A decommissioned submarine base makes a great space for graffiti art.

The vast chamber inside this abandoned cooling tower looks like something out of a sci-fi dystopia.

The world's largest historic armory was established by independent citizens to defend themselves from the wars of larger forces.

This chilly Canadian hotel has a four-month lifespan due to the unusual material it's made of.

Few other hotels can rival the grandeur of the Castle in the Rockies.