France, officially the French Republic (French: République française), is a unitary semi-presidential republic in Western Europe with several overseas territories and islands. Metropolitan France extends from the Mediterranean Sea to the English Channel and the North Sea, and from the Rhine to the Atlantic Ocean. It is often referred to as l’Hexagone ("The Hexagon") because of the geometric shape of its territory. It is the largest country in Western Europe and the third-largest in Europe as a whole, and it possesses the second-largest exclusive economic zone in the world, covering 11,035,000 km2 (4,260,000 sq mi), just behind that of the United States (11,351,000 km2 / 4,383,000 sq mi). Over the past 500 years, France has been a major power with strong cultural, economic, military and political influence in Europe and around the world. During the 17th and 18th centuries, France colonised great parts of North America and Southeast Asia; during the 19th and early 20th centuries, France built the second largest colonial empire of the time, including large portions of North, West and Central Africa, Southeast Asia, and many Caribbean and Pacific Islands.