road weaves in and out of the two counties. The ridgetop portion of the route ends at the junction with State Route 92, because this northern area of the Santa Cruz Mountains is a protected watershed owned by the San Francisco Water Department. Highway 35 is co-routed with SR 92 for 2 miles (3 km) east, descending towards Crystal Springs Reservoir, which it crosses on a causeway, and then joins Interstate 280 northbound for 6 miles (10 km). However, on the southbound side, Route 35 exists as a separate road to the west of the freeway between Bunker Hill Dr. and Route 92, as there is no connector road between 280 South and 92 West. Route 35 departs from 280 at the southern end of San Bruno, running to the west of the freeway, regaining the ridgetop separating South San Francisco and Daly City from Pacifica. It crosses State Route 1 in Daly City and in San Francisco, Skyline Boulevard ends and the highway briefly continues along Sloat Boulevard until it reaches its terminus when it intersects Highway 1 again at 19th Avenue. SR 35 is part of the California Freeway and Expressway System, but is not part of the National Highway System, a network of highways that are considered essential to the country's economy, defense, and mobility by the Federal Highway Administration. SR 35 is eligible for the State Scenic Highway System; however, only the portion from the Santa Cruz–Santa Clara County line to the SR 92 junction is officially designated as a scenic highway by the California Department of Transportation, meaning that it is a substantial section of highway passing through a "memorable landscape" with no "visual intrusions", where the potential designation has gained popular favor with the community. Recreational use Because of its scenic views and winding roadway, Skyline Boulevard and surrounding roads see substantial recreational motoring and bicycling use. Many sports cars and motorcycles can be found congregating near the intersections with State Route 9 and State Route 84, particularly on weekends. Mountain bikers are also commonly found at the many trailheads along the road. Several public open spaces border on Skyline Boulevard, including Sanborn County Park, Windy Hill, and the Purisima Open Space; both the latter are parts of the Midpeninsula Regional Open Space District. Numerous hiking trails originate from parking lots off Skyline in these open spaces. Whenever there is snow on the road's