The park occupies a narrow valley carved by Penitencia Creek through the western foothills of the Diablo Range. The canyon floor is surprisingly lush, with woodlands, lawns, and picnic areas shaded by sycamores and oaks. The mineral springs that gave the park its early fame emerge from rock formations along the creek, leaving rust-colored and white mineral deposits on the stones. Thirteen miles of trails range from level paths along the creek to steep switchbacks climbing to the South Rim Trail and North Rim Trail, where views open across the Santa Clara Valley to the Santa Cruz Mountains on the opposite horizon.

In the late nineteenth and early twentieth centuries, Alum Rock Park operated as a kind of public spa. Visitors soaked in mineral baths, drank from the various springs, and promenaded along the canyon. A steam railroad once carried passengers from downtown San Jose to the park entrance. That era has passed, but the park retains its character as a place of restoration, if not the medicinal kind. Today's visitors find a visitor center, a small museum and animal rehabilitation facility, playground equipment, sand volleyball courts, and designated areas for creek play where children wade in Penitencia Creek on warm afternoons.

Alum Rock Park sits in the Alum Rock district of San Jose's east side, a part of the city that has historically received less attention and investment than its western and southern neighborhoods. For the communities surrounding it, the park functions as a backyard wilderness, a place where families can access nature without driving to the coast or the mountains. The 720 acres offer enough variety to sustain repeated visits: the canyon floor for casual outings, the ridge trails for exercise, the creek for summer play, and the mineral springs for quiet contemplation of the geological forces that created the landscape.