The eclectic observatory castle of a 19th-century astronomer and explorer.

The facade of this 16th-century building is decorated with carvings of 300 seashells.

A hidden medieval crypt where a famous legend says the devil used to teach black magic.

The Cathedral of Salamanca has a number of unusual carvings but none so surprising as a modern astronaut.

This magnificent castle grew from a small Moorish fortress, and reportedly inspired two iconic Disney castles.

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

These "mermaids" that surround a plaza in Segovia are rather sphinx-like.

A curious memento mori hangs in the magnificent Cathedral of Segovia.

Construction of Barcelona’s iconic (but controversial) church was finally completed in 2026—a century after the death of its architect.

A beautiful but toxic fountain of mercury.

An early 20th-century bullring converted into a modern shopping center.

A resort destroyed by a mysterious bombing offers visitors only its remains and the riddle behind it's demise.

A breathtakingly steep set of stairs is carved directly into the face of the sea cliffs of Bonifacio.

This weird, elephant-shaped rock also hosts two ancient tombs.

A striped 12th-century basilica sits in the countryside of Sardinia.

Stalactites and stalagmites in a beautifully lit cave.

Ancient cave tombs known as the "houses of fairies."

The titular "little arch" near this Italian resort is one of the most popular diving spots in the country.

This elaborate hole in the ground was built as a sacred site for an ancient civilization.

A former mining village that now operates as an open-air museum.

This one-of-a-kind archeological site is home to strange prehistoric ruins, the original use of which is still a mystery.

Monument to the area's potato and lamb industries.

An eerily charming collection of salvaged buildings and curios grown out of a family scrap business.

A quirky hardware store filled with museum-worthy cars and motorcycles, including a motorcycle that set a land speed record in 1967.