The Pillars of Hercules is the ancient name for two huge rocks that stand on either side of the Strait of Gibraltar, which separates Spain from Africa.
The waters of the Atlantic Ocean flow east through the strait into the Mediterranean Sea.
One of those rocks is Gibraltar, a territory of the United Kingdom; the other is Jebel Musa in Africa.
The Rock of Gibraltar is a huge limestone promontory that lies on a peninsula off the coast of southern Spain.
Gibraltar is only 2.5 square miles (6:5 sq km), but its prime location on the Strait of Gibraltar has long made it a valuable piece of land for military reasons.
The British took Gibraltar from Spain in a 1704 war.
Spain would like to have Gibraltar back, but so far the United Kingdom has refused to return it.