Reinhardt Redwood Regional Park @ Oakland Hills Near Chabot Space Center

Park near Trudeau Training Center and you can pick up either the Serpentine Trail or Dunn Trail to start the hike. The entire hike is roughly 4 miles round trip around the loop where you will see wild poppy blossoms covered the grass in spring will walk through the tall redwoods and get a good glimpse of the entire East Bay and San Francisco at at the top of the mountain. 

There's also a recreational area where they offer pool and volleyball courts and picnic areas for groups and families. However, that will be a different parking area near Roberts Regional Recreation Area.