Mission Trails Regional Park is one of the largest urban parks in the USA.
As elucidated in Wikipedia:
The park consists mostly of rugged canyons and hills, with both natural and developed recreation areas, including many beautiful flowers. It is the seventh largest open space urban park in the United States consisting of 6,150 acres (24.9 km2). The highest point is 1,592 foot (485 m) high Cowles Mountain, which is also the highest point in the city of San Diego. The San Diego River flows through the park. A one-way access road goes through the park, allowing hikers, bikers and pedestrians on one side and cars on the other. The park is open every day of the year.
The park has over forty miles of hiking, mountain bike and equestrian trails, a rock climbing area, a campground adjacent to a small lake. There is also the modern 14,000-square-foot (1,300 m2) Mission Tails Regional Park Visitor and Interpretive Center. It includes a number of exhibits, a library, a 93 seat theater that includes a Blu-ray projection system with a large screen.
The Visitor Center also includes an art gallery where award winning artists display up to 55 photos and paintings. New artists display their talent every month. The most popular trail of the park is the Cowles Mountain trail, which takes hundreds of people per day to the summit for a breathtaking 360 degree panorama of San Diego County. Another popular stop is the Old Mission Dam, which was built to supply irrigation water to the Mission San Diego de Alcala, the first of the chain of missions established by Junípero Serra in California. Another popular destination within the park is Lake Murray, a reservoir supplying water to San Diego neighborhoods. It is also home to the Kumeyaay Campground which consists of 46 rustic campsites, and the Equestrian Staging Area(Multi-use) Staging Area.