This charming, hidden guild museum holds some 700 years of crossbow history.

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

The largest bell in the world has been swinging high above a Cologne cathedral for almost a century.

A church filled with the bones of hundreds of virgins martyrs—or so they say.

The final resting place for a wealthy Roman family, this tomb might be the best preserved of its kind outside Italy.

A beautiful maze marks where three countries meet.

This bakery and museum offers tours of the tastes and mythology of Aachen's signature spice biscuit—just don't ask for the recipe.

A collection of weird and wonderful art fills a former houseplant nursery.

Part modern art project, part traditional chapel, this see-through church is only substantial from the right angle.

This "floating railway" is one of the world's oldest monorail systems.

A medieval gate once used as a prison and how home to a city museum.

This historical Netherlands fortress still bears the marks of its single siege.

This centuries-old gothic monster has been converted into a sprawling, glossy bookstore.

The ruins of this Dutch castle sit atop a labyrinth of once-secret tunnels and passageways, dating back over 900 years.

No need to strap in for a "ride" on this walkable roller coaster.

The Belgian library displays burned books that were salvaged from the fires of both world wars.

A giant bug impaled on a 75-foot-tall needle.

This unique bridge physically lifts a piece of the road into the air to let boats pass by.

The tallest church in Mechelen might have been the tallest in the world if not for a lack of funds.

This steel frame is a skeletal mirage of a lost 16th-century stone building.

A 1:20 scale piece of the Netherlands commissioned by a queen lets visitors take a stroll as giants.

Nestled in the woods lies this land art project: a hybrid between park, maze and natural monument.

A 14th-century fortified keep showcases the masterpieces of an ingenious 20th-century clockmaker.

Take a walk in a recreation of ancient Rome.