Quito, formally San Francisco de Quito, is the capital city of Ecuador, and at an elevation of 9,350 feet, it is the highest official capital city in the world. It is located in north-central Ecuador in the Guayllabamba river basin, on the eastern slopes of Pichincha, an active stratovolcano in the Andes mountains. With a population of 2,239,191 according to the last census, Quito is the second most populous city in Ecuador, after Guayaquil. It is also the capital of the Pichincha province and the seat of the Metropolitan District of Quito. The canton recorded a population of 1,842,201 residents in the 2001 national census. In 2008, the city was designated as the headquarters of the Union of South American Nations.The historic center of Quito has one of the largest, least-altered and best-preserved historic centers in the Americas. Quito, along with Kraków, were the first World Cultural Heritage Sites declared by UNESCO in 1978. The central square of Quito is located about 25 kilometres south of the equator; the city itself extends to within about 1 kilometre of zero latitude. A monument and museum marking the general location of the equator is known locally as la mitad del mundo, to avoid confusion, as the word ecuador is Spanish for equator.