Indian Rock in Sanborn-Skyline County Park is a classic Bay Area crag near Castle Rock State Park. Offering about a dozen sport and toprope routes ranging from 5.8 to 5.12a, Indian Rock, a large sandstone boulder typical of the region, has enough to keep you busy for an afternoon and several fun climbs that will bring you back for more.
A safe, walk-up top rope anchor with two solid bolts is available on the eastern edge of the north face of the crag, and it can be accessed by wrapping around Indian Rock on the right side while approaching from the main trail. This anchor serves the fun classics, Vicious Circles (5.10d) and Blowing Bubbles (5.9). Other top rope anchors are available on the west side of the crag via a short scramble.
On the sunnier south face of the crag, another popular route accessible to many climbers is the eponymous South Face (5.8+), a short but satisfying slab climb that will help newer climbers learn to commit to tiny holds. It is possible to scramble to set up a top rope on this route, but it can also be comfortably led, with the first bolt reachable from a secure ledge at the base of the route and rappel rings on the anchor bolts to allow a simple clean. For more advanced climbers, Krokus (5.11d) and Donkey Dong (5.11d) are perennial favorites.
For all the details on Indian Rock routes, "Bay Area Rock," a local favorite guidebook authored by well-known photographer Jim Thornburg, covers the crag well.
The free parking area is about 100-200 yards south of the main entrance to Castle Rock State Park on Skyline Boulevard. Following the main trail about a quarter-mile straight into the park will lead you to the crag.
Note that the park asks climbers not to climb within 48 hours of rain to avoid damaging the rock after it has been softened by showers.