The gap between them is the “corner” in the old grant’s name, Rinconada de los Gatos. El Sereno, 2,580 feet, gives Monte Sereno its name; the San Andreas Fault runs in the valley just south of it, and signs at its preserve warn of cougars.
El Sombroso, 2,999 feet, is part of the Sierra Azul Open Space Preserve, whose trails climb from Lexington Reservoir.