The province of Callao is built on and around a peninsula. It is the main port of Peru. A historical fortress, Castillo de Real Felipe, stands on the promontory overlooking the harbor. A large naval base is sited in Callao. Callao has several islands: San Lorenzo (currently a military base), El Frontón (a former high security prison), the Cavinzas, and the Palominos, where numerous sea lions and sea birds live in a virtually untouched ecosystem. Residents of Callao are known as "chalacos". Callao's professional football teams are Sport Boys and Atlético Chalaco.