Watch for raptors, if they are there, climb somewhere else
Castle Rock is an approximately 150' slab of limestone with routes on the usually sunny west face and most recently, the more shady north face. There is a mix of slab, face, crack and arete climbing. Most routes are bolted, but some are mixed and now thanks to Tom, there are a few great gear routes. All routes have two bolt anchors. The rock quality varies from mostly bullet hard on the west face to some loose, blocky stone on the north. Most of the large stuff has been cleaned but the occasional loose stone can still be encountered. Chances are if you head to Castle Rock you'll have the place to yourself.
Hwy. 299 to Burnt Ranch. Turn south on Underwood Mountain Road and travel 3.5 miles. Turn right on 5N40. Drive up this road staying on the most prominent path at all intersections for about 6 miles, passing the parking area for the Trinity Aretes. At this point look for a road to the right at a hairpin turn. This road is blocked by a large log and a ditch. Park here and head down the road on foot until you reach a dead-end at a large cul-de-sac. At the cul-de-sac, turn and head north on a faint climbers trail across a tree covered slope. The trail can be hard to see in places and has some very loose footing in places. After about five minutes you'll reach Castle Rock.
More precise directions: (1) Take a right on Underwood Mountain Road if heading east on Hwy 299. Set your odometer to zero. (2) At 4.0 miles, take a right on 5N40 Rd. (3) At 6.2 miles (from 299) you'll pass by the Trinity Aretes. (4) At 9.5 miles, park on your right at a small turnout/old road, that is closed by a large berm. (5) Hike down the road for about 5 minutes. The road ends at a large cul-de-sac. Just before reaching the cul-de-sac, look for a culvert on your right. Head straight up to the ridgeline and over, eventually skirting the left side of Castle Rock to the base. About 5 minutes from leaving road to the base. (6) Alternatively, you can basically side-hill from the cul-de-sac, but it's steep and loose.