San Diego, California, the state's second largest city and the seat of San Diego County. It is about 100 miles (160 km) southeast of Los Angeles and lies on San Diego Bay (an arm of the Pacific Ocean), one of the finest natural harbors in the United States.

Centered on the northern end of the crescent-shaped bay, San Diego extends for some 30 miles (48 km) along the coast and spreads over hills and valleys to the north and east. Elevations of 1,000 to 1,600 feet (300 to 490 m) above sea level are reached in hills in the eastern part of the city.

Southernmost San Diego—separated from the rest of the city by the suburbs of National City and Chula Vista—touches the Mexican border. Other principal suburbs adjoining San Diego are La Mesa, El Cajon, and Imperial Beach. The resort town of Coronado lies on a peninsula across the bay from downtown San Diego.