San Francisco East Bay residents actually have a volcano in their backyard at Sibley Volcanic Regional Preserve. Originally called Round Top Park, Sibley shares with Temescal and Tilden Parks the distinction of being one of the East Bay Regional Park District's original parks.
The Sibley backpack camp is a small, primitive hike-in site for a maximum of 15 campers (although this would be super cramped in my opinion, unless it a bunch of small kids), a moderate 0.2 mile walk from the parking lot (NO VEHICLE ACCESS). The site has basically 360 degree views of Mount Diablo, Vollmer Peak and Tilden Park. There are only two tent pads - approximately 10'x25' and 10'x20'. Site has 2 picnic tables, 1 serving table, and a pit toilet close by which was very clean and well maintained.
During the day you’ll have lots of people walk semi/sorta by the campground, but there is no reason that anyone would walk through your area as if they did they’d tumble off and down the side of a nice steep hill…
No wood fires or BBQs are allowed; only camp stoves are allowed for cooking, your night time enjoyment.
Drinking water is 0.2 miles from camp at the trail head so keep that in mind before it gets too dark to hike back and forth for a drink.
There are several trails providing tons of access throughout the preserve. The 31-mile East Bay Skyline National Recreation Trail, part of the Bay Area Ridge Trail system, traverses the preserve along the ridgeline between Wildcat Canyon and Anthony Chabot Parks. Round Top Road goes from the Sibley visitor center to the top of Round Top. Round Top Loop Trail circles Round Top peak. Volcanic Trail, once a quarry haul road, contains most of the stops on the self-guided volcanic tour.
Dogs are allowed throughout this section of the park and in camp on leash but are not allowed on the adjacent Huckleberry trails. Also, the EBRPD lists, dogs “must be under owner's control at all times” and must not disturb other animals or park visitors, but I definitely saw a lot of loose well behaved dogs running free.
Bikes are allowed on the fire trail, but there are lots of hikers and dog walkers in this park so be mindful. Also, Horses are allowed but there is no hitching rail and no water troughs in the park (or at least that I saw anywhere).
If you decide to try and bike be mindful that most trails are hiking and equestrian only. A few trails are multi-use. Bicycles are not allowed on narrow-gauge trails, except on the Skyline Trail between the Sibley visitor center and Old Tunnel Road. Bicycles are allowed on the wider-gauge fire trails and paved roads but are not allowed on Sibley Round Top from EBMUD water tank road junction to top of Round Top Peak.
Vehicles must be parked in the staging area and display a valid overnight parking permit: 3 parking permits are included in the reservation and will be mailed 5 days in advance. No additional parking permits are available. Otherwise, you can actually get here via public transport by Taking the AC Transit CB bus to the Mountain Blvd stop, them walk about 3 miles to the park.
While you can check if it’s already reserved online. Reservation must be completed at least 5 days in advance by calling 1-888-EBPARKS or 1-888-327-2757, press option 2.