Spanish architects used seized Muslim gravestones to rebuild parts of the fortress.

London's creepiest cemetery was once the site of dueling magicians and mobs of stake-carrying vampire hunters.

This huge metal monument is slowly being stripped to its concrete skeleton.

A chain of 16 wondrous lakes formed as a result of the gradual dissolution of soluble layers of bedrock.

A whimsical bridge adorned with decorative dragons.

This one-time health resort was used by aristocrats around the world.

Two stone columns flank the grand Venice square, but there were supposed to be three.

Go inside to really appreciate this 500-year-old technological masterpiece.

This Venice bookstore has resigned itself to constant flooding by keeping its books in bathtubs and boats.

Ancient ruins hidden underneath a modern luxury hotel.

The martyr's wax-enhanced skeletal remains lie preserved in a glass case in the Santa Maria della Vittoria in Rome.

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

The celebrated eyesore created by starry-eyed sweethearts.

High atop the Eiffel Tower is a small apartment built exclusively to entertain the science elite and make the rest of Paris jealous.

Paris' linguistic guide to the international language of, yes, love.

This sweet-toothed bear searching for snacks has been a symbol of Madrid for decades.

A stone slab in Madrid marks the point from which the distances of Spain's national roads are measured.

For decades, Puerta del Sol has been illuminated by a giant, guitar-wielding bottle of sherry.

Abandoned for decades, trains still pass through the now-restored remains of one of Madrid's first metro stations.

One of the most spectacular bridges in Spain spans a narrow chasm that divides the city of Ronda.

This underground church is topped with a 500-foot cross that is seen by many as a beacon of fascist hubris.

This charming, medieval walled village is Spain's first "book town."

A majestic hotel for dreamers rises from the center of a fairytale wood.

Natural stone arches form a walkable "cathedral" at low tide, then disappear entirely when the water returns.