This 3.5-mile loop hike was an exploration in Diablo Foothills Regional Park with a short section in the City of Walnut Creek’s Shell Ridge Open Space. Part of the area near the trailhead is designated as Castle Rock Recreation Area, which has historically specialized in picnic space for large groups. This was my first visit to Diablo Foothills Regional Park, and I met a friend at the Castle Rock Staging Area for a relatively short, but pretty, loop hike with nice views of nearby open space including hills robed in winter-spring green.
The GPS track shows an overview of the loop; the orange dot designates the Castle Rock Staging Area, the start/end point.
The hike is rated is Moderate, with just over 700 feet of elevation gain and loss.
From the Castle Rock Staging Area a trail climbs up the hillside just a short distance before a T junction with Castle Rock Trail. We turned right to traverse the loop in a counterclockwise direction. Almost immediately there were nice views across a small canyon toward the lower reaches of Mt Diablo State Park. From this location the primary and North Peak summits were not visible; however, Eagle Peak and Mitchell Rock were visible at the right and left, respectively, in the picture. This initial view seemed to provide an apt setting for a park named Diablo Foothills!
Before long we were overtaken by a handsome horse and its rider.
Many of the park’s oak trees drop their leaves in the winter, making clumps of mistletoe stand out.
We continued around the loop, first west and then south along Borges Ranch Trail, with a short section on paved road near the Old Borges Ranch Interpretive Center, which is in Shell Ridge Open Space. In general, the boundaries between open spaces managed by different agencies are almost invisible, with a modest sign, perhaps a fence with a gate, and perhaps a small kiosk with different park brochures. At the interpretive center there are several ranch buildings containing exhibits. One of these buildings housed, among other items, a wagon mounted on a wall.
After briefly exploring the buildings we continued along Borges Ranch Trail, once again unpaved. As we left the ranch area we saw a bunny having a snack in one of the grassy areas.
About 0.2 mile past the end of the paved road there is a 4-way trail junction, where Briones Ranch Trail becomes Twin Ponds Trail and the Briones to Mt Diablo Regional Trail (also the Mokelumne Coast-to-Crest Trail) crosses. We turned left on the Briones to Mt Diablo Regional Trail. From the junction there was a nice view generally to the west toward what I consider to be the back side of the East Bay Hills. Across several rows of hills the distinctive silhouette of Round Top, in Robert Sibley Volcanic Regional Preserve, was visible.
About 0.3 mile past the previous junction the Fairy Lantern Trail comes in from the left, and after another 0.2 mile the Buckeye Ravine Trail also comes in from the left. We continued straight, with a slight descent, and had a lovely view ahead (southeast) of the green hills and the continuation of the Briones to Mt Diablo Regional Trail.
We noticed that there was what looked like a social trail that climbed up a small hill to our left, and we decided to climb up and check out the view. We were treated to perhaps our only view of the main part of Mt Diablo, though it was almost unrecognizable other than some communication towers near the top, I think due to the perspective of looking up at it from relatively close range. Below was our first glimpse of the sandstone formations known as Castle Rock.
We returned to the main trail and almost immediately came to another junction with Buckeye Ravine Trail, which descends rather steeply down the ravine, losing about 300 feet in 0.4 mile (14% grade). Since we hadn’t brought hiking poles, we needed to exercise some care to descend safely.
At the lower end of the ravine Buckeye Ravine Trail tees into Stage Road Trail near Pine Creek. We turned left on Stage Road Trail. Almost immediately we noticed some striking, almost orange, fungi growing in the moist ground-level vegetation. This specimen was at least 6” across!
Along Stage Road Trail, almost a fire road, there were interesting rock formations and quite a few more hikers than we had encountered elsewhere. After about 0.4 miles the Fairy Lantern Trail entered from the left, and then a single-track trail split off from Stage Road Trail. We decided to take the single-track trail, Castle Rock Trail, since it would also end up at the staging area and would probably have less foot traffic. Since it was a little higher on the hillside, the views were better also. One of the nice views was behind us, with more interesting rocks in the Castle Rock formation.
Another pretty view was this one, of a spring-green-carpeted hill with several scattered oak trees. The late afternoon lighting was from the side and was, I thought, especially pretty.
We completed the loop just uphill from the Staging Area parking. My friend and I had selected Diablo Foothills Regional Park for our hike because we thought it would be pretty – neither of us had hiked there previously – and we were certainly not disappointed. For a longer hike, it would be straightforward to complete a loop at least twice as long by continuing to the southeast part of the park.