An untouched lava tube accessible to the adventurers.

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

This Roman arena once played host to bloody gladiatorial battles.

Peek into a cave of giant, glimmering crystals.

Indigenous cultures believed all life would end if this enormous rock toppled.

A series of well-preserved ruins show the culture of the ancient Benehoaritas people.

Stop by, and you'll receive a map to two well-preserved ancient petroglyph sites.

Possibly the oldest masonry dam in all of Europe.

Marvel at this massive waterspout fueled by the incoming tide.

The highest peak in mainland Spain is said to be the final resting place of a Muslim king.

A fiery-red region of scooped out land still largely untouched by civilization, tourists or otherwise.

Walls of stone rise up from sinkholes caused by underwater erosion.

Locals use these rock pools and waterfalls for swimming and cliff diving.

Two large eyes painted anonymously on a mountain overlooking the city pay homage to an old legend.

Whimsical sculptures and caves chiseled by nature over the millennia.

The walls of these four caverns are filled with art that dates back to the earliest human presence in Europe.

These striking ruins of a castle resemble a ship's stern.

This Arab fortress was once the largest citadel in Western Europe.

The largest medieval water tank on the Iberian Peninsula is preserved beneath the Cáceres Museum.

"Satisfying" is a good way to describe these beautifully aligned rows of Spanish mills.

An arresting arch punched straight through a mountain provides one of the most scenic spots, and challenging climbs, on the planet.

A breathtaking and biodiverse wilderness in the mountain setting of Ernest Hemingway's "For Whom the Bell Tolls."

Hundreds of caves once used to store grains and animal feed.

This 7,000-year-old megalithic wonder covered by a Franco-era reservoir emerges in times of drought.