Over thousands of years, this slot canyon was carved out of the bed of an ancient lake.

A giant, Gilded Age mansion that once belonged to the beer baron of Milwaukee.

One of the largest collections of wildlife art in the United States, built into the side of a cliff in rural Wyoming.

Hidden well off the beaten path in Catalonia is this crumbling medieval castle that is slowly being covered in graffiti.

Bold black and white motifs of life and death add a dramatic flair to this 17th-century crypt.

A statue commemorating the island's tradition of dancing dwarves in Napoleon hats.

A road that winds through this natural cave is the only way to access the small, appropriately-named village of Cuevas.

The four-story mural is the centerpiece of a lavish hotel's lush atrium.

An uninhabited village that preserves and documents rural architecture and an endangered way of life.

Peek into a cave of giant, glimmering crystals.

A surrealist labyrinth and museum of contemporary sculptures.

A cemetery in Barcelona's Poblenou district is home to this touching funerary statue, which depicts death in the form of a winged skeleton.

This Gothic church houses ornate royal tombs and a magnificent gilded altarpiece.

Remnants of the rich history of fish salting in this ancient Mediterranean port town.

Medieval ruins nestled within a breathtaking swath of Spanish nature.

Originally used to sell brandy, the bull-shaped billboard became an iconic symbol of Spain.

The ruins of a 2,000-year-old Roman fishing village perched on one of the best beaches in Spain.

The most elaborate of 12 medieval arched doorways to the old city of Burgos.

This home designed for chocolate magnate Antoni Amatller is an exquisite treasure-box of Catalan Modernism.

Salaguti's live-in museum: a fortress against criticism and consumer art.

A delightful museum devoted to the history of books.

An old wool-washing house filled with Fluxus contemporary art.

Down this yellow brick road, visitors are treated to toadstool houses and massive mushroom sculptures.

The walls of these four caverns are filled with art that dates back to the earliest human presence in Europe.