This is one of my favorite loops in Joseph D. Grant County Park in the hills east of San Jose.
It starts at Halls Valley Lake and... more » climbs steeply into the nearby hills along the Yerba Buena Trail (with a highly recommended side trip to McCreery Lake). It turns at the Canada De Pala Trail and returns on the Halls Valley Trail.
Along the way you'll see sweeping vistas of the nearby Diablo Range along with the observatories atop Mount Hamilton, the highest peak in the South Bay. Wildlife sightings are common: hikers have spotted coyotes, turkeys, bobcats, feral pigs, tarantulas and even the occasional mountain lion.
In springtime, this is one of the best wildflower locales in the Bay Area. Summer's too hot but winter's great (if muddy) and fall is interesting when the tarantulas come out.
The park sits on lands once owned by a prominent ranching family (hence the informal title "Grant Ranch"). The hiking can be arduous -- many of the rails were built for people on horses rather than on foot -- but what you can see along the way makes it worth every arduous step. less «