Historic medieval fortified city in southwest France.

The ruins of a bombed medieval village memorialize the destruction of the Spanish Civil War.

Haunting monument to the German Jewish philosopher who died while fleeing fascism.

This French castle is said to have once held the Holy Grail but is now a gorgeous mountaintop ruin.

Giant eggs, walls of bread, and nightmare surreality mark the largest collection of works by Salvador Dalí.

Famed architect Antoni Gaudi built this generous thank you gift to a friendly host who housed him during a job.

Religious dwelling in a Spanish volcano.

Stunning Roman aqueduct used for 1900 years and still standing.

A Romanesque tower appears when water levels drop.

This ancient Spanish castle sits high upon a hilltop.

Mine shafts and hard pastries await visitors at this massive mountain of salt.

Tower that was a frequent stop on the travels of King James I.

Living towers made of people that are now recognized by UNESCO.

An enchanting monastery in the Spanish countryside appears lifted from a fantasy tale.

Holy Grotto of Montserrat Monastery holds one of Europe's mysterious black Madonnas.

This whimsical winery by Antoni Gaudí looks ripped from the pages of a fairytale.

A gravity-defying "devil's bridge" that has a surprising architectural feature for its stability.

Mountain where Jesus was first tempted by the Devil.

Gaudí's famously flamboyant architectural style is on full display in this sprawling park and garden.

A beautiful but toxic fountain of mercury.

Week-long block party becomes a competition for the best decorated street.

Barcelona's historic 19th-century sewers, whose foundations were laid in medieval times, are open to the public for exploring.

For one day every month Barcelona's Estació de França transforms into a market for model trains.

A vista of the city and sea from atop the little-known viewing deck on an unassuming Columbus statue.