The Tijuana Estuary is the largest coastal wetland in Southern California and it is located on the international border between the U.S. and Mexico. Tijuana Estuary is considered to be a very unique part of the National Estuarine Research Reserve System. The Reserve offers four miles of walking trails, taking visitors into prime bird watching areas and down to the river mouth where the Tijuana River meets the Pacific Ocean. Visitors may explore the park on their own or join one of the free guided nature and bird walks on weekends.