Sibley Volcanic Regional Preserve

On Skyline Blvd., just east of Grizzly Peak Blvd./Diablo Dr. Oakland, CA

Robert Sibley Volcanic Regional Preserve is located in the Berkeley Hills of the East Bay Area of the San Francisco Bay Area, California. The Park is part of the East Bay Regional Parks District (EBRPD), covers 928 acres (3.76 km2) and is located partly in Alameda County and partly in Contra Costa County, east of Oakland. You can enter them on Skyline Boulevard from Oakland or on Old Tunnel Road from Contra Costa County.

The Park was one of the first three parks established by the East Bay Regional Parks District (EBRPD) in 1936. It was originally called Round Top Regional Park. Round Top (height 1,761 feet/537 m) is an extinct volcano in the Berkeley Hills. It is home to at least two stone mazes of recent origin. The park was renamed after Robert Sibley, the second president of the EBRPD, shortly after his death.

Round Top, one of the highest peaks in the area, is made up of lava and volcanic debris leftover from a 10 million-year-old volcano. Over the past 10 million years, massive tectonic forces on the Hayward and Moraga earthquakes have lifted the Berkeley Hills, folded the rock formations and tilted the Round Top volcano complex on its side.

Softer sedimentary rock from the Orinda Formation was eroded and the Round Top volcano was exposed. In addition, the quarrying in the north half of the reserve revealed cross-sections of the rock geology, providing an unsurpassed outdoor laboratory for the study of volcanism in the Central Coast Ranges.

The untapped visitor center of the Skyline Boulevard staging area displays the geology of the preserve. A self-guided brochure is available in the staging area that highlights the geological features of the preserve.

Several trails provide access to the entire preserve. The 31-mile East Bay Skyline National Recreation Trail, part of the Bay Area Ridge Trail system, runs along the ridgeline between Wildcat Canyon and Anthony Chabot Parks. Round Top Road goes from the visitor center of Sibley to the top of the Round Top. Round Top Loop Trail Round Top Circle.

Most of the trails are hiking and horseback riding. There are a few trails that are multi-use. Dogs are allowed at Sibley but are not allowed on the adjacent Huckleberry trails. The visitor center in the park displays self-guided tour brochures so that guests can stroll around the park and learn about its historic significance at their own leisure.

Bicycles are not permitted on narrow-gauge trails, except on the Skyline Trail between the visitor center of Sibley and the Old Tunnel Road. Bicycles are allowed on wide-gauge fire trails and paved roads but are not allowed on Round Top Road from a fork 15 miles east of the visitor center to the top of Round Top.