An eerie, derelict amusement park in Berlin.

One of the most poignant ruins of the Chernobyl nuclear disaster, the local football team's stadium has been quickly reclaimed by nature.

These lush botanical gardens employ the most purrfect pest control force.

Monument to a suicide protesting the Soviet invasion.

The tunnel's elegant proportions keep you snug with no claustrophobia freak-out.

Europe's second largest ossuary wasn't discovered until 2001.

A steampunk-styled three-floor factory churning out art, activism, and electronic beats.

Around 100,000 bodies are buried below the medieval headstones, many of which mark graves with multiple bodies stacked up to 12 deep.

Two stunning 17th-century libraries and a cabinet of curiosities.

An odd museum dedicated to French fakes.

Original cabaret handbills, posters, and feline artwork are a purrfect highlight of the Museum of Montmartre.

This unusually shaped mountaintop tower looks like a UFO floating over the city.

The bizarre visions of H.R. Giger, tucked away in a Swiss medieval city.

An overgrown and largely forgotten cemetery lies hidden within the outskirts of Amsterdam.

Noirish green neon marks the location of one of the oldest private detective agencies in France.

The first green space constructed on an elevated viaduct.

Paris' fabled purveyor of exotic taxidermy and natural history curios.

This charming cobbled backstreet is the most Instagramable street in Paris, much to the residents' annoyance.

The vast, legendary catacombs hold secrets much stranger than stacked bones.

Abandoned railway line circling the city of Paris.

One of the largest cat sanctuaries in North America is considered a "Club Med" for felines.

A tribute to an iconic act of defiance from the Croatian War of Independence involving a small car.

These pools have been abandoned for over 20 years.

This 16th-century monastery has been turned into a surrealist architecture compound.