Walk into an underground archeological dig, the site of the Roman Forum that was once the center of Valencia.

With a facade that measures just 107 centimeters, this five-story building is one of the skinniest in Europe.

Earth's rocky history has rarely glittered so brightly as it does in this Spanish museum.

Five million people are laid to rest here, more than the population of Madrid itself.

A small museum displays some of the artifacts discovered during a subway station renovation.

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.'

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

The remains of this misplaced church were moved here stone by stone.

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

Once the grandest synagogue in medieval Spain, it now stands as a memorial of the 15th-century Jewish exile.

A subterranean relic of the Spanish Civil War hides below this picturesque park.

Running under an entire mountain, the longest highway tunnel in North America is kept fresh using portal fans and jet fans.

The remains of the second-oldest zoo in Europe can be seen within these library gardens.

Automatons that were once removed after one fell from the building.

Once a resting spot for King Fernando VII.

19th century pendulum and a clock restored by a rogue group of guerilla artists.

This is the oldest Roman-made bridge in the city still existing in its original state.

Giant topiary dog once played a role in a terrorist bomb plot.

Allegedly haunted by Walt Disney himself, this inconspicuous lamp is always kept lit in his honor.

Inspiration struck on this seat outside the Griffith Park merry-go-round.

A rare set of strings by famed instrument maker Antonio Stradivarius is on display in the Royal Palace.

Known as the Casa de las Siete Chimeneas, this haunted 16th-century manor has a dark, mysterious past.

Originally used to sell brandy, the bull-shaped billboard became an iconic symbol of Spain.