The 13 mile keyhole loop through Las Virgenes and Cheeseboro Canyons from the Ahmanson Victory trailhead is a classic Southern California mix of multi-use fire roads and single track trail.
The segment from Shepherd’s Flat down through Cheeseboro Canyon is especially popular, and on the weekend you’ll find an assortment of hikers, runners, mountain bikers, and sometimes an equestrian group or two. Even on a warm day, the oak-shaded sections of the canyon can be surprisingly comfortable.
Here’s a Google Earth image and Cesium browser View of a GPS trace of the loop, and links to trail maps for Upper Las Virgenes Canyon Open Space Preserve (formerly Ahmanson Ranch) and Cheeseboro/Palo Comado Canyons.