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

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

Turntable anonymously received orphans, alms, and groceries.

Commonly acknowledged as the only public monument to the Devil himself.

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

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

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

Madrid's romantically ornate crystal palace has been offering shelter to plants and art for over a century.

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

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

A beautiful but toxic fountain of mercury.

Three bridges and one giant canyon make up this fantastic Spanish settlement.