Alum Rock Park is located in a canyon in the Diablo Range foothills on the east side of San Jose. The park offers 13 miles (21 km) of trails, varying from fairly level along Penitencia Creek to sharp switchbacks climbing to the ridges to the South Rim Trail and the North Rim Trail. The narrow floor of the canyon includes a visitor center, picnic areas, a playground, and sand volleyball pits.
An easy hike with shaded trails almost all the way. The sound of water flowing through the creek can be very soothing to the ears. If you get a chance to get close to the water, you'll find that it's very clear and you might even spot fishes scurrying about!
Parking is paid and the parking area is usually not very busy, except when groups or families book the picnic grounds for a party.
The trail is understandably dry and dusty this time of the year, but the views from the hill-tops are quite amazing. The trails can be very narrow, especially in the switchback routes, but overall the risk level is not high. If you hike before noon, you'll find that most of the south rim trail is shaded. Elevation is also okay, but it can get somewhat steep in the switchbacks.
Christine I. on Alum Rock South Rim Trail
Very nice for beginners or moderate hikers.
Nice shaded trail with medium incline. The view is excellent through out. Also nice picnic area in the starting point suitable for group activities and barbecues.
By the way the first three parking lots are free and the third (closer to trail) is paid.