Spain's unique Mosque-Cathedral has been a place of worship for both Muslims and Christians throughout its history.

This 86,000-square-foot artwork is the largest mural in the world to cover a dam.

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

The first mechanized factory in Spain is also one of the most significant mints in the history of money.

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

Poet Antonio Machado's former residence offers the quintessential Castilian lifestyle of the provincial towns in the early 20th century.

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

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

A controversial art piece that harkens back to local folklore.

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

Meant to resemble a massive tree, the building is the best example of Spanish organicist architecture in Madrid.

This girder was hit by a bomb during the Spanish Civil War, but nobody knew about it until 2016.

Over two centuries old and counting, Madrid's massive botanical garden contains one of Europe's only desert environments.

A reproduction of the famous prehistoric cave paintings is hidden underground at the National Archaeological Museum.

This influential Renaissance-era library was once the haunt of kings and monks.

This underground church is topped with a 500-foot cross that is seen by many as a beacon of fascist hubris.

This enigmatic artifact is a rare depiction of an ancient Iberian noblewoman.

This embalmed man is one of the best preserved mummies from the Canary Islands.

An iconic and controversial ancient Iberian funerary urn with a hauntingly penetrating gaze.

These ancient artifacts are a testament to the enduring significance of the bull in Spanish culture.

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

Once a resting spot for King Fernando VII.

Stuck in the middle of a modern Madrid city block are the remains of a 19th century sports complex.

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