[2] The ridge is 5 miles long, and runs from the northwest to the east, dividing Novato's Ignacio Valley and San Rafael's Lucas Valley, and separating Novato from central and southern Marin County.

Big Rock Ridge is the second-highest point in the Marin Hills, which in turn are a part of the California Coast Ranges.

Much of eastern Big Rock Ridge is public land, with the Lucas Valley and Ignacio Open Space Preserves covering much of the foothills.

[3][5] The easiest way to the top is the 6.7 mile Big Rock Trail, which opened in 2003 when George Lucas donated 800 acres of land to create the Lucas Valley Open Space Preserve.

The southern slope is much more varied when it comes to soil types, but they all share a high runoff class and a land capability classification of 7e.