Old San Juan is located on a small and narrow island which lies along the north coast, about from the east end of Puerto Rico, and is united to the mainland of Puerto Rico by three bridges. It is bounded by the Atlantic Ocean to the north and to the south by San Juan Bay (or "Bahia de San Juan")—which lies between the city and the mainland. On a cliff about high, at the west end of the island and commanding the entrance to the harbor, rise the battlements of Fort San Felipe del Morro, in which there is a lighthouse.