Round Valley is a small regional park on the outskirts of Brentwood. The park is near the edge of the Diablo Range and its wooded hills contrast with the starkly treeless flatlands of the nearby Central Valley. Somewhat unexpectedly, the dry environment here at the eastern edge of the mountains has produced some exceptionally attractive oak groves. The patchy hillside groves are unusually open, with small, widely-spaced oaks on a lawn-like grassland with little or no understory.
The Hardy Canyon Loop starts out in one of these groves and climbs to an open, high grassland with nice views of Round Valley. It's the longest and most scenic singletrack trail in the region, which makes it a real treat; most regional park trails are dirt roads, which usually aren't as enjoyable as singletrack.
The other popular route in the preserve is the flat Murphy Meadow loop, which circles around Round Valley itself. This loop is mostly used by cyclists and horseback riders; although scenic, the flat dirt roads are a little dull for hiking.
The Antioch/Brentwood area is one of the most rapidly developing areas in the Bay Area and, compared to the rest of the Bay Area, is currently a little underserved with regional parks. More parks are being developed, but in the meantime, Round Valley is very busy on weekends; it's not unusual for the parking lot to completely fill up and on a nice day you might encounter a group of hikers every 5 minutes or so.
Start at the parking lot off Marsh Creek Road. Just after crossing the large bridge over Marsh Creek, turn left onto the Hardy Canyon Trail, which starts out as a dirt road before changing to singletrack. The trail skirts a large, flat meadow, then enters an oak grove and and begins to climb. Although it's excessively worn from over-use, the trail is otherwise very scenic, especially near the bottom of the climb. Further up, the canyon narrows and the woods get less interesting.
The trail abruptly breaks out of the woods and climbs an open, grass-covered hillside. There are some limited views down the canyon with glimpses of the Central Valley beyond. The trail reaches a broad saddle, the high point of the hike. An unofficial trail to the right climbs steeply up to a ridge with much better views of the Central Valley.
As the trail starts to descend on the other side of the saddle, it offers some great views of Round Valley below, one of the highlights of the hike. The descent is on a grassy slope dotted with an occasional oak. The trail to the floor of Round Valley and ends at a dirt road, the Miwok Trail.
The Miwok Trail is the least attractive part of the park. Although it runs through oak woods, the road is wide and heavily worn from over-use, and the valley bottom that it passes through has a worn-out look from cattle grazing. The well-used unofficial trails that run alongside the road are a little more attractive. There are a few small hills to climb on the way back to the parking lot. A prominent unofficial trail to the left bypasses an odd little loop where, for no obvious reason, the road switchbacks steeply up the hillside and then descends again.
Most people hike this loop in the opposite direction that I've described, which results in a much better finish to the hike. However, I kind of like the clockwise direction because it puts the climbing at the beginning.
© 2015 David Baselt