A rooftop restaurant hides in plain sight atop Vienna's Palace of Justice.

This sublime architectural marvel is a rare example of an expressionist church.

A museum filled with tiny, adorable versions of the mighty Royal Danish Navy.

Beneath Denmark's Højbro bridge, a bronze merman and his seven sons forever mourn for the mother and wife who left them for land.

Opulence and fantasy collide in this royal chair which is supposedly made with unicorn horns.

Copenhagen's celebrated theme park and gardens.

Physicist’s epitaph provides final confirmation to a career of turmoil.

This cubist Vienna church building looks like some sort of alien stonehenge.

A magnificent waterfall is also home to the remains of a Roman hydraulic engineering system.

Rome's semi-secret peephole vista is also a former Crusader stronghold.

This hidden Art Nouveau courtyard is an opulent feast for the eyes.

A master of trompe-l'oeil creates a stunning, tourist-fooling dome out of a flat ceiling.

Architectureal fantasy quarter of Rome.

Hundreds of lucky felines haunt the ruins where Caesar was murdered.

The romantic garden was the epicenter of the Hungarian art scene in the 1880s.

A scandalous Art Nouveau collaboration that set Paris all atwitter at the turn of the century.

One of the oldest medical collections in Europe focusing on rare surgical instruments.

A horde of stray cats rule in this secluded Parisian cemetery under a bridge.

This massive library holds what was once the largest book collection in the world.

France's most famous cemetery, with some of its most curious tombs.

The beautiful baroque library of the Hapsburg empire.

The graveyard is filled with beautiful funerary art and boasts breathtaking views of Florence.

Legend says this mysterious stone head belongs to a woman who was petrified by an alchemist.

Nestled in the hills of Tuscany are gorgeous, multicolored hot springs.