A floating cat sanctuary on an Amsterdam canal.

Historic fortifications form the boundary of Vatican City, but it’s not entirely surrounded by walls.

Hidden beneath the famous St. Peter's Basilica is a veritable city of the dead that may hold the remains of St. Peter himself.

The walls and streets of the ancient city are peppered with penises.

Erotic art covers the walls of the largest ancient pleasure palace.

The last moments of the ill-fated Pompeiians, frozen forever in plaster.

This tipsy office building in downtown Prague was originally called “Fred and Ginger.”

Macabre astrological automaton clock dating to the late 1400s.

Baroque celebration of the end of the Great Plague of Vienna.

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

An ode to a soldier who came to town, fell in love, then began making his own sparkling wine.

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

The former Nazi concentration camp stands as a museum to remember this dark chapter in European history.

Inside this Krakow church, an explosion of psychedelic color.

St. Mary's features one of the most spectacularly decorated cathedral interiors in all of Europe.

An artificial date palm stands as a memorial to Warsaw's Jewish community.

This enormous 32-foot painting depicts Poland's greatest medieval battle in glorious detail.

The giant statue and its model solar system honor the native Pole who declared that the Earth revolves around the Sun.

The Polish capital has had a deep connection to its guardian mermaid for almost a millennium now.

Germany's Glienicke Bridge has a shady history of clandestine meetings, espionage, and spycraft.

The "Prussian Versailles" that is as glorious today as when it was built.

The mystic whose incorrupt corpse still attracts the faithful.

Thousands of tourists and residents in Cologne affix "love padlocks" on the Hohenzollernbrücke Bridge to symbolize their affections.

This Dresden church was purposely rebuilt Protestant after being demolished in World War II.