Located south-east of Pleasanton, Sunol Regional Wilderness presently only has developed climbing at Indian Joe Caves, but other opportunities appear to exist as well. There's a pretty wide variety of rock types in the park, but Indian Joe caves is meta basalt. While approaching the area, you can see some rocks on the top of a hill west of the main entrance, this is called flag mountain and appears to have climbing on it, though development has been discouraged because of concerns it would disrupt raptor nesting. There's a $4 entrance fee and the gate gets locked a little after dusk (9 p.m. in August), though camping is permitted in the park.
A pile of meta basalt rocks, Indian Joe caves offers top roping, bouldering and the occasional trad lead on formations reaching up to 40 feet. The holds tend to be either angular or crimpy and the climbing can be anything from slab, cracks, chimney, impressive aretes, or overhung faces. There's also a wide range of existing climbs, 5.3 to 5.12c. There is also the potential for several climbs with difficulties considerably higher.In the summer, Indian Joe Caves get pretty warm and it would be wisest to avoid climbing the routes that get sun, as the black rock absorbes the sun's heat and makes climbing almost unbearable. Fortunately, there's always a handful of climbs that never get sun and therefore are a lot cooler than their brighter counterparts.
From the 680-580 interchange, take 680 south 8 miles to the highway 84/Calaveras road. Go left on Calaveras and follow it past where the speed limit drops to 25. Shortly after the speed limit change go left (4.3 miles from the turn onto Calaveras) on Geary Road. Shortly thereafter you'll reach the fee station.
After entering the park, pass the first left turn (about 50 yards in), which heads to the visitors center, and park just beyond on the left side of the road next to a trailhead (about another 50 yards). Hike across the wooden bridge over a stream, and head right at the junction. Continue another 50 yards until you come to Hayfield Road (which you're not allowed to drive on... though bikes and horses are permitted). Go left on Hayfield road and walk up the road for .8 miles. There's an obvious sign directing you to Indian Joe Caves, follow it right, you'll be able to see the crag up the hill on your left a little ways down this smaller trail. This will meet with the Indian Joe Creek Trail and continue up hill for another ~300 yards until you arrive at the crag. The first landmark is the tallest rock, with a sharp arete on the right, the arete is Orange Arete (11a) and the face is Little Eiger (12c). Paths circumnavigate the climbing area, and most of the warm-up stuff is reached fastest by going clockwise around the area to the backside.
This route chimneys the obvious crack that separates the two bolted rocks on the far (north) side of the area. Many people simply don't bother with pro, when we were there a group of poeple climbed the chimney with tennis shoes on, but didn't go to the top, as there is a bailout to the left (the start of the 5.12c and 5.11a climbs on the southeast side of the rock) 15 feet shy of the top of the route....[more]Browse More Classics in CA
The top report mentions possible climbing on Flag Hill, which is off to the right from the parking lot. Years ago I went to investigate the climbing on this hill, but found the rock just crumbles in your hand. This sandstone type rock is different from the very solid rock found at Indian Joe Caves.