This extinct volcano rises above Edinburgh and is special for its panoramic views over the city.

Enter this small nook and you'll be surrounded by 360 degrees of street art.

A book bound in the skin of an infamous criminal, along with countless other specimens.

Ruined 11th century abbey built by King David I in Edinburgh, Scotland.

17th century streets hidden under Edinburgh were once a breeding ground for the black death.

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

This Hungarian castle was built out of cardboard and wood until it proved so popular that it got upgraded to stone.

Vienna's underworld of tunnels and subterranean rivers made an iconic appearance in a 1949 Orson Welles film.

Dine amidst exotic plants at this former royal greenhouse.

Located right outside of Vienna, visitors can take in expansive views of an ethereal forest.

The topiary maze at the Habsburg hunting lodge.

Macabre museum devoted to historical Viennese murders.

A tropical paradise just a short trip from the opera house is filled with beautiful winged creatures.

What started as a tongue-in-cheek shrine is now a full-blown museum celebrating "The Hoff" and his longtime love affair with Berlin.

On the Spree bank, discover one of the last reminders of a symbolic wall that divided, and was torn down by the people.

A wunderkammer of mysterious objects and stories.

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

This 22-floor tower's Skydeck offers panoramic views of Amsterdam.

Museum preserving torture methods from the past.

The world's only museum devoted to the wonders of fluorescence.

In Chicago, a pizza-enthusiast has opened a museum dedicated to the history of pizza.

This $3 million model train takes you through Chicago, Seattle, and the thousands of miles in between.

Each of these gorgeous, intricately decorated rooms is painstakingly crafted to the scale of 1 inch: 1 foot.

Four glass boxes hover over 1,000 feet in the air to give visitors an unparalleled view of Chicago.