It's not surprising that newspaper magnate William Randolph Hearst once considered Mount Diablo as a site for a sprawling resort. The 3,849-foot peak east of San Francisco is the highest in Contra Costa County, with views that rival those of Hearst Castle on the central coast of California.
Thankfully, Hearst's money and energy were directed elsewhere, and in 1931 the mountain and its rolling foothills were preserved as Mount Diablo State Park. Today, the 20,000 acre, oak-studded park lures hikers with diverse trails that range from wide roads through shaded canyons to steep climbs up tall ridges.
The large sandstone formations of Rock City, on the south side, create a natural playground. Climb Sentinel Rock with the help of stairs carved into the side and a cable handrail.
Black-tailed deer and gray foxes are common, but visit in fall to catch a glimpse of Mount Diablo's most famous creature: the tarantula. And don't forget that view. On a clear day at the summit, you can see the Golden Gate Bridge, the San Joaquin River Delta, Mount Lassen, and even—with binoculars—Yosemite's Sentinel Dome.