At the bottom of this cave is the legendary home of the Gates of Hades–the Underworld–in Greek literature. This area was considered the end of the known world. It is the juncture where Hercules crashed through the Isthmus as he tracked across the Atlas Mountains to complete one of his last labors. In his impatience he pulled apart the land mass between Gibraltar and Tangiers, creating the Strait where the Atlantic and the Mediterranean...