The first urban National Wildlife Refuge in the US sprawls across 30,000 acres of salt marsh, tidal sloughs, mudflats and rolling hills at the southern end of San Francisco Bay. More than 280 species of waterfowl, shorebirds and migratory birds live, breed and/or feed in the refuge, which was dedicated in 1972 and renamed for a former congressman in 1995.From the bluff-top Visitor Center, an extensive system of trails follows boardwalks and bridges across tidal flats. Within the center are excellent interpretive exhibits on life in the refuge, as well as an auditorium and observation deck. More trails extend through managed wetland habitat from an Environmental Education Center (Los Esteros Rd., Alviso; from Rte. 237, turn right at Zanker Rd. for 2mi; open year-round Sat-Sun 10am-5pm; call to verify; 408-262-5513).