and Point Loma fault zones are part of the San Andreas Fault system. About east of the bay are the Laguna Mountains in the Peninsular Ranges, which are part of the backbone of the American continents. The city lies on approximately 200 deep canyons and hills separating its mesas, creating small pockets of natural open space scattered throughout the city and giving it a hilly geography. Traditionally, San Diegans have built their homes and businesses on the mesas, while leaving the urban canyons relatively wild. Thus, the canyons give parts of the city a segmented feel, creating gaps between otherwise proximate neighborhoods and contributing to a low-density, car-centered environment. The San Diego River runs through the middle of San Diego from east to west, creating a river valley that serves to divide the city into northern and southern segments. During the historic period and presumably earlier as well, the river has shifted its flow back and forth between San Diego Bay and Mission Bay, and its fresh water was the focus of the earliest Spanish explorers. Miguel Costansó, a cartographer, wrote in 1769, "When asked by signs where the watering-place was, the Indians pointed to a grove which could be seen at a considerable distance to the northeast, giving to understand that a river or creek flowed through it, and that they would lead our men to it if they would follow." That river was the San Diego River. Several reservoirs and Mission Trails Regional Park also lie between and separate developed areas of the city. Notable peaks within the city limits include Cowles Mountain, the highest point in the city at ; Black Mountain at ; and Mount Soledad at . The Cuyamaca Mountains and Laguna Mountains rise to the east of the city, and beyond the mountains are desert areas. The Cleveland National Forest is a half-hour drive from downtown San Diego. Numerous farms are found in the valleys northeast and southeast of the city. In its 2013 ParkScore ranking, The Trust for Public Land reported that San Diego had the 9th-best park system among the 50 most populous U.S. cities. ParkScore ranks city park systems by a formula that analyzes acreage, access, and service and investment. Communities and neighborhoods The City of San Diego recognizes 52 individual areas as Community Planning Areas. Within a given planning area there may be several distinct neighborhoods. Altogether the city contains