Between Solana Beach and Encinitas, this is the most complex of the estuary systems in San Diego North County. A 7-mile network of trails surrounds the 979 reserve, where more than 700 species of plants, fish, and birds (many of them migratory) live. Be sure to stop by the LEED-certified gold New San Elijo Lagoon Nature Centre. The center, open 9 to 5 daily, offers museum-quality exhibits about the region and a viewing deck overlooking the estuary. Docents offer free public walks every Saturday at 10 a.m.