A medieval village holds a very modern hotel.

The chefs at El Diablo use heat generated by an active volcano to cook the food.

Devastated landscape used for hundreds of years by the Romans as their primary mining site.

Stunning Roman aqueduct used for 1900 years and still standing.

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

Cursed swimming pool left abandoned is now a favorite of filmmakers and ghost hunters.

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

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

The former 1920s mansion of a prominent Catalan developer was used as the Soviet Embassy during the Spanish Civil War, and there is still a bunker below the garden.

Construction of Barcelona's iconic (but controversial) church is expected to be completed in 2026—a century after the death of its architect.

These secluded and abandoned anti-aircraft defenses have become one the most scenic viewpoints in Barcelona.

Gardens representing parts of Asia, Europe, and the Mid East are tucked away among the Soviet-style buildings in East Berlin.

Someone loved this song enough to carve all of its lyrics onto a tree trunk in a Berlin park.

A traditional U-Bahn station in Berlin gets a string of rather untraditional benches.

The world's first clock to use set theory as a measure of time required the invention of a new light bulb just to maintain its obtuse measurements.

This conical hill was built as a testing ground for an engineer known as the Glider King.

A state-of-the-art medical facility from the Imperial era is now a derelict ruin.

A museum dedicated to a Cold War era sausage.

The largest free-standing aquarium in the world resides in a hotel lobby in Berlin.

Started as a kitchen garden, now the second largest botanical garden in the world.

A collection of abandoned typographic signs from Berlin and beyond.

An abandoned NSA listening post on Berlin's "Devil's Mountain."

This futuristic German spa allows visitors to float in a pool of salt water while zoning out to underwater techno.

An extraordinary museum devoted to the pop art legend created by Slovak artists.