Part of the wall is preserved in the aptly named Parque de Berlín in Madrid.

Across Valencia lie the remains of three ancient fortifications built centuries apart: a Roman enclosure, an Islamic expansion, and a medieval Christian wall.

A controversial art piece that harkens back to local folklore.

A tunnel commissioned by ‘the Intruder King’ to escape from the palace if there were problems.

A stone slab in Madrid marks the point from which the distances of Spain's national roads are measured.

A Roman bridge closed to car traffic in the 1990s now open to foot traffic.

The former Nazi Germany concentration camp stands as a museum to remember this dark chapter in European history.

An underground city of salt.

This giant sculpture recalls a famous passage from “Alice in Wonderland.”

The world's largest wooden structure.

Check the time in 145 countries at once with this East German relic.

Few symbols capture the spirit of Catalonia more vividly than its tradition of human towers.

Five mysterious spheres in the wall of a church that puzzle Málaga’s locals.

This tree, over 500 years old, was planted by Columbus’s son.

Its appearance in "Game of Thrones" may spur on the long-awaited restoration of this medieval shipyard.

The final resting place of the great navigator, or maybe his brother.

A small but stubborn relic of Spain’s turbulent past hides in plain sight.

This larger-than-life lime green gummy bear sits in the middle of a roundabout in Spain.

This taberna has been frying up crunchy salt cod since 1860.

A home for Spain's version of the Tooth Fairy, hidden in an old gas company register.

A statue honoring the tragic heroine of a Spanish literary masterpiece.

Mural dedicated to one of Spain's favorite cartoonists, Francisco Ibáñez.

The only urban monument in the world designed by the great surrealist painter Salvador Dalí.

Baltasar Bachero became a hero after he saved the lives of two children nearly run over by an out-of-control mule-drawn carriage.