As you are pulling in, from the parking lot take the left fork of the trail on what looks like an old logging road. Walk around the cable gate blocking motor vehicles from entering and proceed down the trail for roughly 1/8th of a mile. Down in the valley to your right, you will see a mass of boulders scattered around the forest. Most of them are covered in moss and uncleaned. Move past this mass of boulders until you stop seeing them. On the very edge on one side of a steep valley is the Hidden Valley boulder. It is difficult to see from the trail as the climbable side is facing down towards the valley and the top meets the elevation of the ground.