This mine is home to the largest man-made hole in Europe.

Model Trains and Much More in Hamburg.

Hamburgers are intensely proud of their tunnel beneath the river.

This iconic Parisian bookstore doubles as the "Tumbleweed Hotel" for traveling writers.

The largest underground church in Europe.

Once a 19th-century brasserie, this McDonald's exterior celebrates Alsatian design and the "King of Beer."

A marble Lucifer hides behind the pulpit of this Gothic cathedral.

The vibrant buildings in the “capital of the comic strip” celebrate the art form that made it famous.

Potato-peeling mannequins, Inca art, and a dangling tuber mobile help trace the history of fries at this Belgian museum.

The prototype for all Nazi concentration camps.

A deer-headed statue that brings together a 12th-century legend and big wave surfing.

The "Little Ones," show Portugal in full miniature splendor.

Europe's largest collection of matchbox designs is a fascinating exploration of the cultural history of the world.

This unique architectural wonder is also tied to one of the 20th-century's most renowned writers.

This crumbling Portuguese ruin overlooks the populace it once ruled.

At night, bats patrol this magnificent 18th-century space in search of book-eating pests.

Elaborate tile work in this railway station tells the story of Portugal.

A stunning 18th-century site where pilgrims ascend by a series of punishing stairs only to return via funicular.

In Portugal, a secluded stretch of untouched natural beauty hides at the bottom of a steep hill.

Picturesque intersection of witchcraft and ancient Christianity.

This restored Portuguese cafe may well be the most beautiful place in the world to grab a Big Mac.

San Gennaro, the patron saint of Naples, greets pedestrians between these narrow city streets.

This medieval city gate is now a blend of the past and the modern world.

This seaside Italian village doesn't just look Escher-esque, it actually inspired the mind-bending artist.