Jesus' footprints and the first catacombs in the world.

A master of trompe-l'oeil creates a stunning, tourist-fooling dome out of a flat ceiling.

This massive underground salt mine now holds a sci-fi theme park in its depths.

This Transylvanian church has changed its denomination four times.

Island wonderland for communist autocrats.

The world's most important buildings shrunk to a tiny size.

An enormous and lavish Gothic church in Czechia.

The world's greatest slide descends 18 stories from this looping mountaintop viewing platform.

An unusual cave filled with rare alien-looking aragonite formations.

From Austrians to Nazis to Soviets, this historic Budapest fortress has a history as complex as the city itself.

This Budapest bar allows drinkers to leave their mark on the walls, floor, and even ceiling.

Possibly the world's largest hourglass only needs to be reset every New Year's Eve.

Sitting beneath an unremarkable residential building is a museum devoted to classic Pinball.

The Habsburgs' royal collections of art and wonders.

The topiary maze at the Habsburg hunting lodge.

An Amsterdam street lined with antique shops each one dedicated to a different obscure collection.

A church of bones, decorated with 40,000 human skeletons.

Once the home of a hermetic monk, this cave now houses a small church.

A trail of iron footwear stands as a monument to the thousands executed along this riverbank during WWII.

A unique hotel for the artistic soul.

This Slovak bridge is known both for its connection to a national uprising and its UFO-shaped eatery.

This Slovakian statue of an emerging sewer worker might just be a bronze peeping tom.

100 year tradition of fist fights, marked by marble footsteps.

A mysterious chasm in the heart of the ancient Roman Forum, the Lacus Curtius was once believed to be a gateway to hell.