Strait of Gibraltar
The Strait of Gibraltar ( Spanish: Estrecho de Gibraltar) is the strait which separates the Atlantic Ocean from the Mediterranean Sea. On the northern side is Spain and Gibraltar, on the southern side Morocco and Ceuta (a Spanish exclave in North Africa). Its boundaries were known to antiquity as the Pillars of Hercules. There are some small islands, like the disputed Isla Perejil, that is claimed by Spain and Morocco.
The Strait of Gibraltar has a very strategic location. Ships that travel from the Atlantic to the Mediterranean and vice versa, pass through this strait overlooked by the Rock of Gibraltar. During World War II, the British controlled the straits from their nearby base. German submarines entering the Mediterranean Sea were effectively trapped, because they couldn't leave on the surface and the undersea currents were too strong to leave underwater.
For a number of years the Spanish and Moroccan governments have been jointly investigating the feasibility of a tunnel underneath the strait, similar to the Channel tunnel between England and France. A new three-year study for a railway tunnel was announced in 2003.
Also, a group of American and British engineers have studied the feasibility of building a bridge to span the straits. Such a bridge would be of a combination suspension-truss design and would dwarf any existing bridge in height (over 3000 feet) and length (15 km).