Rising from the sea like a titanic fin, the Rock of Gibraltar is a primordial sentinel that guards the entrance to the Mediterranean; the European Pillar of Hercules faces its African twin across the Strait of Gibraltar. From its top, the coast of Morocco shimmers in a desert haze, and eagle eyes spot dolphins dancing below. Criss-crossed by centuries-old siege tunnels and UNESCO-listed caves, the Rock has captured the imaginations of artists and would-be conquerors for centuries. A cable car makes short work of the journey to the top, where old artillery batteries and panoramic lookouts are guarded by legions of Barbary macaques.