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

This giant subway sculpture celebrates the fruit that inspired the theory of gravity.

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

This unique sculpture is often overlooked by pedestrians.

It is said that each of the white stones in the red facade of this medieval house represents the head of a murdered Swedish noble.

Stockholm's deepest subway station is also a stunning ecological wonder.

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

This sublime architectural marvel is a rare example of an expressionist church.

Pre-Nazi swastikas adorn the sculpted pachyderms flanking this brewhouse portal.

Danish tourist destination well known for open stalls where vendors sell marijuana on the street.

Floating swimming pool within a moored vessel.

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

The last remnants of a massive medieval wall that once encompassed the city of Berlin.

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

You've probably seen these distinctive orange-tiled columns on the big screen.

A narrow passage next to a cafe leads to a courtyard exploding with murals, tags, and paste-ups.

A beautiful old horse stable hosts one of the largest collections of domestic animal skeletons and taxidermy.

During World War II, the Nazis repurposed this beer cellar to store stolen artwork.

The largest bottled beer collection in the world holds over 22,000 unique beer bottles.

The old observatory in Copenhagen has a spiral corridor used as a racetrack.

Climb to the top of its spiral spire for spectacular views of Copenhagen.

Copenhagen's celebrated theme park and gardens.

Bored potato-guarding Nazis etched their thoughts onto a brick storage building in Copenhagen's Meatpacking District.

These waste baskets play a few risque messages to discourage littering.