Cliffside houses provide a spectacular view from their perch above the valley.

An architect transformed this abandoned cement factory into his castle-like workshop.

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

A temple to modernity, tucked away amid Barcelona's more well known museums.

This Navarrese cave's history of witchcraft and pagan ritual is not just embraced, but recreated each year.

One of the few remaining ancient aqueducts described by Frontinus as 'the most solemn testimony of the Empire.'

A Spanish town built into the cliffs.

A landscape decorated with enormous skull sculptures.

A stately palace has been converted into the world's largest cannabis museum.

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

A Spanish forest is filled with mysterious stone carvings.

This former Baroque palace on the historic Calle Montcada is a rare architectural gem and was once the meeting place of an aristocratic scholarly society.

An isolated village literally built into the crevices and rock formations of a mountain.

Turntable anonymously received orphans, alms, and groceries.

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

At the foot of a waterfall lies a peaceful swimming lagoon and evidence of over 60,000 years of human habitation.

Step inside the first house designed by Catalan architect Antoni Gaudí, considered to be one of the first Art Nouveau buildings.

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

Bask in the 19th century grandeur of an eccentric Freemason millionaire's private gardens.

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

Spanning the El Chorro gorge, this pathway used to be one of the most dangerous crossings in the world.

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

Mountain where Jesus was first tempted by the Devil.

An unusual stroll through gentlemen's erotica demonstrates that pornography is timeless.