Overview:
This route begins at the park entrance off Old Tunnel Road and follows the Bay Area Ridge Trail along Round Top Creek to the Sibley Staging Area. From the staging area, grab a park map and head up to the water tower to tour the park's interpretative features, labeled 1-11 on the park map. The route will take Volcanic Trail through the park's unique landscape and impressive volcanic peaks. Volcanic Trail ends at Quarry Road, a paved road that returns to the parking area off Old Tunnel Road.
Tips:
The section of the Bay Area Ridge Trail between Old Tunnel Road and Sibley Staging Area is a wildlife refuge and therefore dogs must be on leash at all times. This trail follows a creek and is VERY muddy in winter -- not recommended during wet weather. As an alternative, head up Quarry Road and take Quarry trail to the Round Top Loop trail.
You can download a interpretive park map from the East Bay Regional Park website before you head out. I recommend this as the trail heads are not always kept stocked with maps.
Be sure to check out the fascinating labyrinths constructed in the old quarry pits throughout the park. Sibley is full of surprises so take the time to explore along the way!