Pyramid Rock is the farthest south and fifth highest in a group of five Santa Clara County peaks that exceed an elevation of 4,000 feet. It is located four miles southeast of Mount Hamilton and Copernicus Peak, the county highpoint. Mount Isabel stands just two miles northwest of it. The most distant of the group is Eylar Mountain which as the crow flies is some 12 miles to the north. With efficient planning, a four-peak-day that includes Mount Hamilton, Copernicus Peak, Mount Isabel and Pyramid Rock can be accomplished with less than 13 miles of hiking.
Close-up on large rock outcropping on Pyramid Rock
Southern view of Pyramid Rock
Summit and View
Pyramid Rock marks the beginning and most northern point of Castle Ridge, a high ridgeline centrally located upon lands once part of the original Mexican land grant Los Huecos (Spanish for “the hollows”). Los Huecos was a 39,229-acre grant that included all of the Isabel Valley, the San Felipe Hills and Valley and areas as far south as Mount Sizer now within Henry Coe State Park boundaries. Pyramid Rock has gorgeous 360- degree views. The eastern view is particularly striking as it reveals the wide expanse of both Isabel and Upper San Antonio Valleys. Isabel is the closer of the two. A medium-sized blue reservoir lies partially within the length of it. At the extreme eastern edge, a high ridgeline rises in relief over the two valleys with Mount Stakes the highest point on the horizon line. The entire scene has a sublime stillness to it. Witnessed on a moonless night, the valley is utterly black, isolated--devoid of light. The topography to the south is equally pleasing: a labyrinth of named and unnamed canyons, ravines and ridges that include Castle and Bollinger Canyon and Blue Ridge which rolls out into the most northern reaches of Henry Coe State Park. To the west, a step-work of rounded hills gradually drops down into the San Felipe and San Jose Valleys. Through the haze, Loma Prieta tops the distant Santa Cruz Mountains while stellar views of Mount Isabel, Copernicus and Mount Hamilton draw one’s eyes to the north.
Isabel Valley close-up. Looking south from Pyramid Rock summit.
Go around the locked gate. Take notice of a “no trespassing sign” and another that indicates land ownership by University of California Regents. The route from here to Pyramid Rock is straightforward, approximately four miles due south. Both Google Maps and the USGS Isabel Valley Quadrangle show this trail as “Mule Trail.” The first mile is well forested with medium to large-sized oak and pine trees. Look west and you will notice Sulpher Creek gorge below the steep southern slopes of Mount Hamilton. Cross another gate after one-half mile and continue three-quarters mile further to a three-way junction. Go straight, ignoring both a short spur trail off to the right and another segment of Mule Trail that bears left and descends into Isabel Valley. Continue traveling south on Mule Trail as it snakes its way through the chaparral-covered hills. Near the four-mile mark you will see a fence that runs parallel to Mule Trail that separates it from another jeep trail on the west side of the fence. Shortly thereafter the road passes between two oak trees (see photo). Cross over the fence and follow the second jeep trail. Pyramid Rock is visible one-quarter mile to the south. The road dips and rises and then arrives just east of the peak. Notice a massive grey boulder near the base of the peak that vaguely resembles a pyramid shape. Gain the summit by navigating through the chaparral on the southeast side of the peak. The summit has a few moss and lichen- covered outcroppings of small rocks.
Two oak trees at Mule Trail Sign at start of Mule Trail.
Mount Hamilton, 1861
William H. Brewer writing about the first recorded ascent of Mount Hamilton says:
Nearly east of San Jose, some distance in the mountains, is a high peak we wished to reach, being the highest in that part of the Diablo Range. As near as we could judge from our maps, we supposed it nine miles distant in a straight line. It proved over fifteen. Mr. Hamilton went with us. A ride of six miles across the plain brought us to the foot of the ridge. All this is enclosed, in farms, and under good cultivation. Farmhouses, orchards, etc., give it an American look. We then struck the ridge, and on rising, had a capital chance to see this part of the Santa Clara Valley. It is perhaps twelve or fourteen miles wide at San Jose, an almost perfect plain, very fertile, a perfect garden, and much of it in higher cultivation than any other part of California.
This first ridge was about 1,000 or 1,500 feet high. Then we crossed a wide valley, then up another ridge. We had attained an altitude of nearly three thousand feet, when we came upon another deep and steep canyon cutting us off from the peak. Here we left our mules and proceeded on foot about three miles and reached the peak after 4 p.m. The view was very extensive and the day very clear. It was about 4,000 feet high—we made it 4,200 feet—but that is doubtless too high. We could see various portions of the Coast Range, from far above San Francisco to below Monterey, probably 140 to 150 miles between the points, and the Diablo Range for about a hundred miles.
It was five o’clock before we left and after sundown before we got on our mules, with at least fifteen miles to ride. Night closed on us among a labyrinth of hills and canyons twelve miles from camp and at least six from any road. We gave our mules the bridle and let them find the way back, which they did with a sagacity beyond belief, over steep hills, along the ridges, through canyons, to the road at the foot of the hills at the edge of the plain. It was near midnight when we reached camp. [William Brewer, Up and Down California in 1860-1864: The Journal of William H. Brewer. (University of California Press, Berkeley 1966, 1974) pgs. 173-174.
Name of these flowers? Looking north towards Copernicus Peak.
From Interstate 680 in San Jose take the Alum Rock Avenue exit and drive .8 miles to State Route 130/Mount Hamilton Road. Turn right and drive 19 miles up a long, slow and winding road to Mount Hamilton. Pass Lick Observatory and various other buildings in the area. Just past the complex of buildings, a sign reads “Begin San Antonio Road.” Follow it 1.2 miles further and park on the north side of the road at a dirt pullout with room for only one car. Continue by foot 40 yards further down San Antonio Road until you see a gated road which is the Mule Trail. To approach from Interstate 580 in Livermore, take the North Livermore Avenue exit south to Mines Road, which becomes San Antonio Valley Road, and continue on to Mount Hamilton, a distance of 50 miles.
Mount Isabel and Sulpher Creek Fenceline.
External LinksPyramid Rock summit stats.
List of Santa Clara County Peaks
Isabel Valley Quadrangle link
Pyramid Rock is private property so you'll need permission from the property owners to hike here.
Santa Clara County has a number of camping options. The closest campground is Joseph Grant. Here is a useful link.