It houses the remains of a 17th-century version of the Titanic.

A hidden bathhouse in one of Stockholm's oldest and busiest neighborhoods is open to anyone who can find it.

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

An illuminated manuscript comprising the life's work of a lone monk, inexplicably decorated with a portrait of Satan himself.

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

You haven’t properly toured a winery until you’ve slept in an actual wine barrel.

In addition to fine dairy products, the world's most beautiful milk shop also offers a feast for the eyes.

Where once there was a train station bathroom, there is now this German burger joint.

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

A whimsical and twisted animatronic monster tour beneath the streets of Berlin.

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

This jaw-dropping 19th-century bridge uses its reflection to form what appears to be a perfect circle.

An eerie, derelict amusement park in Berlin.

Aged nearly 1,700 years, the world's oldest bottle of wine is probably still drinkable.

An old department store turned Nazi prison turned artist commune.

An abandoned swimming pool decays on the outskirts of Berlin.

The music is over at the Ballhaus Riviera Ballroom, but the ballroom remains in haunting disrepair.

This classic restaurant features a gorgeous mirror-clad room.

A state-of-the-art medical facility from the Imperial era is now a derelict ruin.

A decomissioned facility where the German "Transrapid" maglev trains were once tested.

A stunning gilt bronze relief denounced by Hitler as "degenerate art"—even though it was dedicated to the Nazi leader.

Renowned mathematician and physicist Carl Friedrich Gauss once worked at this observatory.

A collection of antique telescopes dot the halls of the university's astrophysics department.

While you wait to cross the street at a traffic light in Mainz, you might notice that the light is staring back at you.