Callao is the largest and most important port in Peru

Peru

Peru , officially the Republic of Peru , is a country in western South America. It is bordered on the north by Ecuador and Colombia, on the east by Brazil, on the southeast by Bolivia, on the south by Chile, and on the west by the Pacific Ocean....

. The city is coterminous with the Constitutional Province of Callao, the only province

Province

A province is a territorial unit, almost always an administrative division, within a country or state.-Etymology:The English word "province" is attested since about 1330 and derives from the 13th-century Old French "province," which itself comes from the Latin word "provincia," which referred to...

 of the Callao Region. Callao is located west of Lima

Lima

Lima is the capital and the largest city of Peru. It is located in the valleys of the Chillón, Rímac and Lurín rivers, in the central part of the country, on a desert coast overlooking the Pacific Ocean. Together with the seaport of Callao, it forms a contiguous urban area known as the Lima...

, the country's capital, and is part of the Lima Metropolitan Area

Lima Metropolitan Area

The Lima Metropolitan Area , is an area formed by the conurbation of the Peruvian cities of Lima and Callao. It is the largest metropolitan area in Peru, the eighth largest in the Americas, and among the thirty largest in the world. The conurbation process started to be evident in the 1980s. The...

, a large metropolis

Metropolis

A metropolis is a very large city or urban area which is a significant economic, political and cultural center for a country or region, and an important hub for regional or international connections and communications...

 that holds almost one-third of Peru's population. Callao borders Lima Province

Lima Province

Lima Province is located in the central coast of Peru and is the only province in the country not belonging to any of the twenty-five regions. Its capital is Lima, which is also the nation's capital....

 on the north, east and south, and the Pacific Ocean on the west.
Callao was founded by Spanish colonists in 1537, just two years after Lima (1535).