The city spreads from the mostly flat lowlands near San Francisco Bay into the foothills of the Santa Cruz Mountains, which rise to more than 600 feet (180 m) above sea level in Crestmoor and more than 700 feet (210 m) above sea level in Portola Highlands. San Bruno City Hall sits at an official elevation of 41 feet (12.5 m) above sea level.
Portions of Mills Park, Crestmoor, and Rollingwood are very hilly, featuring canyons and ravines. Creeks, many of them now in culverts, flow from springs in the hills toward San Francisco Bay. Just west of Skyline Boulevard and outside of city limits is San Andreas Lake, which is one of several reservoirs used by the San Francisco Water Department, providing water to San Francisco and several communities in San Mateo County, including San Bruno west of I-280.
San Bruno City Park, bordered by Crystal Springs Avenue and El Crystal School, is the major municipal park. It offers shaded walkways and hiking trails, picnic tables, a playground, a small ballpark, a municipal swimming pool, and a recreation center. Junipero Serra County Park, also accessible from Crystal Springs Avenue, is a 100-acre (405 square kilometer) park owned by San Mateo County and includes numerous hiking trails, as well as picnic shelters, barbecue pits, and picnic tables.