The world's largest single-aperture telescope resides in the Canary Islands.

The largest and best preserved necropolis in the Western Mediterranean.

Designed in the Romanesque style, this structure was once a fortress monastery.

The history of this Moorish castle includes royals, a Mexican-Spanish association, and several attempts at lodging.

Tower that was a frequent stop on the travels of King James I.

Marvel at this immense work of art that greets arrivals to the city.

Hidden underground, a remarkable 10th-century bath complex survives virtually unaltered.

A reservation-only highland forest reserve of endangered Pinsapar firs stands above a village in Andalucía.

The ruins of the second-largest circus school in the world.

This air raid shelter from the Spanish Civil War is now a museum dedicated to the history of the city's bombardment.

Get a close-up look at a 16th-century Basque whaling ship at this factory and museum.

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

A large collection of solar and night-time telescopes dot a small area on the Teide mountain range.

The four-story mural is the centerpiece of a lavish hotel's lush atrium.

The last of three massive blast furnaces that were once at the foundation of the Port of Sagunto economy.

The spectacular geological formations make it one of the most impressive caves in Europe.

This rough experimental house was created by flooding a dirt hill with concrete.

Built on the foundations of an ancient Roman villa, the unique architecture of this castle on the Catalan coast was used as a set for 'Game of Thrones.'

This exhibition space designed to look like the skeleton of a whale is hidden underground.

This abandoned racetrack looks like it is set to hold competitions in the apocalypse.

This 15th-century aqueduct with distinctive pointed arches was used for irrigation in the Vinalopó valley.

The legendary bathing site of a Moorish queen is actually part of a Roman fish farm.

Remnants of the rich history of fish salting in this ancient Mediterranean port town.

This ancient amphitheater was restored in the early 1990s.