Santa Rosa Plateau Loop
Distance: 11 miles (loop)
Hiking Time: 6 hours
Elevation Gain: 700'
Directions: From Interstate 15 in Murrieta, exit southwest on Client Keith Rd. Drive 6.9 miles. Clinton Keith changes names to Tenaja. At a stop sign, stay left onto Via Volcano. In another 0.8 mile, park along the side of the road at the Vernal Pool Trailhead.
This trip offers a grand tour of the Santa Rosa Plateau including the vernal ponds, the historic adobes, and the volcanic mesas, culminating with a panoramic view from Monument Hill. If you have a full day to hike, this is a great way to see many of the diverse features in the reserve. The trail also features fine views of San Jacinto Peak, San Gorgonio Man., and Mt. Baldy, the three tallest peaks ringing the Los Angeles Basin. There are many variations possible, so you can shorten or lengthen the trip as you prefer. For example, you could start or end at the visitor center, and could extend the hike to include the Los Santos Trail and/or the Sylvan Meadows Loop.
From the Vernal Pool Trailhead, hike 0.6 mile east through a meadow dotted with oaks, passing the Los Santos and Trans Preserve Trails, to the big pool, which is full of water after winter's rains. After visiting the boardwalk along the pool, continue 0.9 mile to Ranch Rd. Turn right (east) and hike 0.1 mile to the historic Santa Rosa Ranch, which is good place to stop for a break.
Next, follow the Lomas Trial north along the west side of the ranch for 0.1 mile to a gate marking the entrance to the Adobe Loop Trail. Turn right and follow the creek under the shady oaks for 0.5 mile to a T-junction with the Punta Mesa Trail. Turn left (east) and follow the Punta Mesa Trail down through the chaparral to a small creek crossing, then continue up and north. Pass an intersection in 1.9 miles with Monument Rd. and continue another 0.7 mile across a wide meadow to a junction with the Tenaja Truck Trail. The construction scars on the hills to the northwest show how fortunate it was that this pristine plateau was saved from development.
Turn left (west) and follow the dirt road for 0.5 mile, then turn right and follow Waterline Rd. for 0.7 mile toward the visitor center passing oaks and granite boulders in the meadow. Shortly before reaching the visitor center, turn right on the Granite Loop Trail and go less than 0.1 mile, then turn right again on the Vista Grande Trail. The trail forks but both branches rejoin shortly near a bridge over Cole Creek and a bench overlooking the tenajas. In 0.9 mile, cross the Tenaja Truck Trail again and continue 0.7 mile to a T-junction with Monument Hill Rd. Turn right (west) and climb 0.4 mile to a spur trail that leads 0.1 mile to the summit of Monument Hill (2,046'), where you can take in the views of the entire eastern half of the reserve that you have just explored.
Continue west along Monument Rd., passing two junctions with the Lomas Trail, to reach Ranch Rd. in 1 mile. Turn left (south) and go 0.4 mile. At a junction near Poppy Hill, turn right (west) and hike 0.1 mile toward the hill, then turn left (southwest) on the Trans Preserve Trail. Follow it 0.8 mile to a T-unction with the Vernal Pool Trail on Mesa de Colorado. Turn right (west) and retrace your steps 0.4 mile to where you began this big loop.