Ecuador is a representative democratic republic in South America, bordered by Colombia on the north, by Peru on the east and south, and by the Pacific Ocean to the west. The country also includes the Galápagos Islands in the Pacific, about 965 kilometers (600 miles) west of the mainland. Ecuador straddles the equator, from which it takes its name. The country was part of the ancient Inca empire, colonized by the Spanish, and gained independence through a series of battles from 1820 to 1830. Its capital city is Quito, located in the mountain highlands, and its largest city is the port of Guayaquil on the Pacific Ocean. Ecuador is one of 17 megadiverse countries in the world according to Conservation International. The Galápagos Islands are well known as a region of distinct fauna, famous as the place of birth of Darwin's Theory of Evolution, and a UNESCO World Heritage Site.