The lower trail was muddy and overgrown due to the recent rains, small areas just completely torn-up. The wind was almost unbearable to me for the first hour, but I kept going. Great uphill workout though, and a nice view of both Sierra (in far distance) and Diablo. Park entrance is $6.00.
Quite a hidden gem with some great views if you go while the hills are green. The trail starts and ends with substantial elevation changes. This not a casual stroll. Parts of the trail were overgrown with vegetation. There are lots of cows, horses, hawks and I saw a few coyotes on the trail. Also some good views of Mt. Diablo.
This trail is actually in the park named Round Valley Regional Preserve. However, Round Valley is next door to Los Vaqueros Reservoir, (which is spelled incorrectly as well).
Round Valley Regional Preserve address is:
19450 Marsh Creek Rd, Brentwood, CA 94513