An ancient Roman theatre restored to its former glory in the Spanish city of Cartegena.

The oldest Roman lighthouse still in use.

A historic and oft-filmed prison stands in a Chicago suburb.

This historic Illinois "Muffler Man" has been converted from axe-touting lumberjack to rocket-wielding space ace.

Windblown rock formations in an ancient Roman quarry.

The many—66 to be exact—faces of the German forest.

Tiny castle in the middle of the Rhine made you pay to pass.

A giant floating rubber duck-bunny painted with a different design every year.

On the shores of Lake Garda, the ruins of a Roman villa that allegedly belonged to the poet Catullus.

Once one of the world's great cities, Cahokia was a place of religious worship, trade and mass human sacrifice before being mysteriously abandoned.

Giant topiary dog once played a role in a terrorist bomb plot.

An ancient knight and a symbol of the city's freedom.

An "inside out" building in the historical center of Paris, featuring Europe’s largest modern art museum.

A series of abstract, silly sculptures represent the works of a great modern classical composer.

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

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

This fairytale castle was built as a show of power but was nearly torn down thanks to its history of torture.

This large open-air museum showcases the ordinary lives of the people of the Netherlands and pre-industrial crafts and practices.

An idyllic hotel that gave its name to a supposed shadow government.

A maze of crosses marks the jumbled divide between the Netherlands and Belgium.

The attic of a four-century-old canal house hides a clandestine church.

This museum housed in a former brothel explores the past and present of sex work in Amsterdam.

Amsterdam's former hotspot for public executions and dissections.

Established in 1638 to battle the Black Death, Hortus Botanicus Amsterdam is a treasure trove of rare flora.