Oakland’s Dr. Aurelia Reinhardt Redwood Regional Park has become my absolute favorite in the Bay Area—especially in the summer months when rattlesnakes are prolific in the North Bay. This hidden redwood forest is a beauty, with miles of trails through 150-foot tall, second-growth coast redwood trees. (The old growth forest was extensively logged in the 1850s to supply building materials for the San Francisco Bay Area.)
As with all parks in the East Bay Regional Park District, Redwood Regional Park allows dogs on all hiking trails; some areas require leashes, in particular the Stream Trail that runs along Redwood Creek, protected due to a unique species of salmon. Other trails allow off-leash as long as dogs are under voice control. Cows, sheep and goats are utilized in grazing areas to control vegetation (and therefore, wildfires) so please keep your dogs safely away from these animals.
Redwood Regional is a large park with many trailheads, or “staging areas”, most of which provide trail maps and information kiosks; all of the trails are well-marked. My favorite hike is a 2+ hour beauty that will allow your dog to be off-leash for the first two-thirds, saving the on-leash portion for the end when he/she will be exhausted and ready to walk (leashed) calmly at your side.
Park at the Skyline Gate Staging Area, then take the upper trail to your right (West Ridge) for about 10 minutes, then the French Trail off that to the left. This is all off-leash and through redwood forests, absolutely gorgeous. Follow the French Trail for as long as you want. You can cut back down at the Mill Trail, the Fern Trail or the Chown Trail, all of which lead to the Stream Trail (on-leash here!) back to your car.