This tunnel was built in order to protect the village of Daroca from flash floods during rainy seasons.

The largest cave on the island of Menorca was likely the site of Iron Age rites and rituals.

An open-air museum showing how people on El Hierro lived from the time of the first settlers until the late 20th century.

The cave where Saint Genadio meditated and played chess.

An untouched lava tube accessible to the adventurers.

An otherworldly art experience.

These Bullet-scarred bunkers are haunting reminders of the Spanish Civil War.

This cave was the former seat of power for two brothers who ruled together as kings.

The grotto where Saint Ignatius of Loyola lived as a hermit for nearly a year.

To fit bodies into this Renaissance crypt, they were first left to decompose in the crypt's rotting room.

Sanctuary on a ridge near an ancient shrine to a "Black Madonna" built by the founder of Opus Dei.

Open air sculptures by an eccentric and loin-clothed hermit.

Head to the mountains to catch a glimpse of Spain's endangered subspecies of brown bear.

An unexpected ghost village lurks on the southeast coast of Tenerife.

Eccentric sculpture garden brings Basque mythology to life.

Strange masks and obscure costumes are housed in this old Madrid corrala.

Tour the inside of a massive lava tube formed during a 1949 volcanic eruption.

See replicas of Europe's most famous cave paintings and even some of the animals that feature in the art.

An independent naturist colony amidst 1000-year-old ruins.

A surrealist labyrinth and museum of contemporary sculptures.

This remarkable museum sprung from one of the most important prehistoric archaeological sites in the world.

Peek into a cave of giant, glimmering crystals.

Whimsical sculptures and caves chiseled by nature over the millennia.

The deserted remains of a luxury hotel turned hospital ward.