San Diego . The city is the seat of San Diego County and is the economic center of the region as well as the San Diego -- Tijuana metropolitan area . Tijuana ( [ tiːˈwɑːnə ] ; [ tiˈxwana ] ) is the largest city in Baja California and on the Baja California Peninsula and center of the Tijuana metropolitan area , part of the international San Diego -- Tijuana metropolitan area . The Tijuana metropolitan area , and in Spanish the Zona Metropolitana de Tijuana , is located on the Pacific Ocean in Mexico .
The Tijuana -- San Diego metropolitan area's name is a misnomer, as Tijuana is not located within it.