Hidden Valley Open Space is amazing! A tilted, 1,000 acre grassland bowl at the northwest corner of Windemere development in San Ramon, the Open Space and its creeks drain into Hidden Valley Park. This hike offers spectacular views of Mount Diablo and the Tassajara Valley. Join us to discover this brand new open space – you’ll see soaring raptors and dramatic shadows cast over the picturesque Tassajara Hills. The hike will be a 4 mile out and back with a few hundred feet of elevation gain.