Located well off the beaten track for tourists, this is one of the nation's largest urban parks, a 5,800-acre spread that includes abundant birdlife, two lakes, a picturesque stretch of the San Diego River, the Old Mission Dam (probably the first irrigation project in the West), and 1,592-foot Cowles Mountain, the summit of which reveals outstanding views over much of the county. There are trails up to 4 miles in length, including a 1 1/2-mile interpretive trail, some of which are designated for mountain bike use, and a 46-space campground (tel. 619/668-2748). The park came about in 1974 when the area surrounding Cowles Mountain began to experience a housing boom; city and county representatives worked with Navajo community planners to make an initial purchase of land. In 1989 the first park ranger was hired, and in 1995 the visitor center opened, cementing a place for Mission Trails in the hearts of outdoor-loving San Diegans.