Behind medieval walls in a corner of bustling Palermo is a breathtaking former mosque once inhabited by a wolf-taming hermit.

Monasteries on rock pillars, once accessible only by frayed ropes.

This field of half-buried stone crosses was the burial place of a sect of heretical gnostics.

An ambiguous ambience emanates from this centuries old leprosy quarantine.

An alien landscape on the banks of the Aegean Sea.

The ruins of an abandoned medieval city where the last Byzantine emperor was crowned.

An autonomous republic of Orthodox monks.

Thousands of rusting train cars have been slowly falling apart on the edge of Greece's second largest city.

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

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

What if all public housing projects had been designed by "the Pygmalion of modern architecture," not only their prototype?

The largest falcon hospital in the world, caring for over 6,000 feathered patients every year.

This artificial archipelago was supposed to resemble a map of the world.

This massive steel pyramid can be entered by a set of jagged steps that let visitors stand in its heart.

An industrial relic is now one of Europe's most staggering art spaces.

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

The monumental home of Prussia’s eccentric "Cannon King."

"Purveyors of traditional sweets and vintage treats."

This secluded walkway overlooks a magnificently wild London green space.

Pop culture has helped to keep this iconic British building from being destroyed.

A charming 17th-century alley is lined with secondhand bookstores and antiquarian shops.

A 1,215-foot tunnel transports pedestrians beneath the River Thames.

Several plaster noses are hidden in plain sight around London's Soho neighborhood.

This churchyard arbor is surrounded by hundreds of gravestones placed there by author Thomas Hardy.