Sunol Regional Wilderness lies at the northern end of the Diablo Range that extends 40 miles to the south. Consequently, this area has a feeling of wildness not often encountered on most Bay Area hikes even though there are a lot of cows. Perennial Alameda Creek flows along the western edge of this East Bay Regional Parks District holding while steep hills and ridges rise to the east. The terrain is typical of the East Bay with California buckeye and blue oak along drainages in addition to soft chaparral and grassland everywhere else.
This hike starts at the bridge over perennial Alameda Creek about 100 yards south of the small Visitor Center. This is a loop hike so you can go either way at the T-intersection, but go left for the most pain. The trail is flat as it follows the creek, but soon begins an exhausting climb of 900' over a mile on the Flag Hill Trail. The route is a well-graded fire road, but it never lets up. Up up and some more up. You eventually reach the top of a ridge with a totem-like trail marker, and head left a few hundred yards to a bench and a rocky overlook 200 yards beyond to take a break at the top of Flag Hill.
Return to the trail marker, and go north on Flag Hill Road as it winds along the top of the ridge to a small summit before heading down to a saddle. The small saddle has a few large eucalyptus trees, and shows signs of extensive grazing. It's basically a mess so best to continue up the Vista Grande Road which is signed by another large trail marker. You gained 900' going up to Flag Hill, gave back a few hundred going down to the saddle, and now have to gain 600 more on the way to this hike's highest point. You head up the spine of a ridge even higher than Flag Hill to another bench to meet its junction with the Eagle View Trail. This trail is fairly faint, and heads downhill from the bench and then "catwalks" along the edge of a ridge as it heads into a dense drainage.
You're not going to make it if you fall downhill so keep your eyes on the trail. About 1/3 mile from the bench you reach the bottom of a steep canyon, cross the intermittent creek, and make your way along a rough, loose trail as it contours above the bottom. The trail is very poor in certain stretches with steep downhill stretches interspersed with loose catwalks. You reach the Eagle View Road about 1/2 mile from the bench, and turn right. 1.4 mile later go right onto the Cave Rocks Road (fire road). 1/3 mile later go left onto the Indian Joe Creek Trail. Soon enough the route becomes evenly-graded and moderate all the way to the bottom. The big attraction on the way down is Cave Rocks about 1/5 mile down Indian Joe Creek Trail from its junction with Cave Rocks Road.
Indian Joe Nature Trail is about a mile down from Cave Rocks, and go right for 4/10 mile to the bridge over Alameda Creek. - Feb 26 2012 Jim Lyding