A unique spiral staircase that doesn't quite make it up to the top floor.

An ancient Viking runestone hidden in plain view in Stockholm's old town.

This Stockholm light tower can be controlled by anyone with a smartphone.

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

Sweden's "good old days" painstakingly re-created in a model village.

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

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

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.

Launched by Napoleon's soldiers more than 200 years ago, a cannonball remains embedded in the tower wall.

This spaceship sculpture in the middle of the Slovakian capital looks like it just crash-landed.

Thousands of slain Soviet soldiers are buried within the shadow of this enormous obelisk.

Twisted trees shaped by coastal winds make this woodland look like something from a spooky story.

Soaring over 6,000 feet in the Bavarian Alps, this beer garden was once Hitler's 50th birthday present.

A striking 12th-century-style castle built on the edge of a cliff.

A fascinating insight into daily life in the Eastern Bloc.

Art and a pun, all in one.

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

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

The highest tides in the world come in and out here twice a day, allowing you to essentially walk along the ocean floor.

Uh, pardon me, ma'am, but I couldn't help noticing that there's a Columbo statue in the middle of Budapest.

A graceful natural rock formation stands astride the point where the Gulf of California meets the Pacific Ocean.

Diego Rivera's massive tiled fountain and failed infrastructure project.

No telescopes, no power, no gift shop: The Observatory of Chichen Itza, one of the world's oldest observatories, takes astronomy back to basics.