San Ysidro (Spanish pronunciation: [san iˈsiðɾo]) is a district of the City of San Diego, immediately north of the U.S.-Mexico border. It neighbors Otay Mesa West to the north, Otay Mesa to the east, and Nestor and the Tijuana River Valley to the west; together these communities form South San Diego, a pene-exclave of the City of San Diego, thus making it possible to travel (by water) between central San Diego and South San Diego without ever leaving the city limits.