10.0 miles, Full day
If you're bugged by the existence of a parking lot atop Mount Diablo -- the East Bay's signature peak -- you're probably just the type to check out nearby North Peak, which gets far fewer visitors and offers just as many awesome vistas.
My favorite path to North Peak is definitely the hard way: five miles and over 3,000 feet of climb on some of the steepest trails in the Bay Area. The struggle has rewards beyond knowing you've walked from near sea level to one of the highest accessible points in the region. In springtime, the hillsides light up with wildflowers; in winter, rains cleanse the skies so you can see the snow-capped Sierra peaks hundreds of miles away; in autumn, tarantulas prowl the trails in search of mates. Summer's about the only time when it's too hot to attempt this hike.
This hike also has a bonus: a jaunt along the Mount Olympia Trail, notorious as one of the steepest in the Bay Area.
If you've got the legs for it, this is among the East Bay's must-hike routes. For peak-bagging purists, a hike to the main summit adds another three miles and 800 feet of elevation gain.
This is a truly strenuous hike; don't try it if you're not up for long miles with lots of climbing and tricky terrain. Watch for poison oak on narrow single-tracks. Rattlesnakes may dwell in rocky areas. If you see one, give it plenty of distance.
What to Bring:
A map, available at park entrances and from the State Park Store
Plenty of water; there's none on the trail (it can be filtered from streams, but only in winter and spring, before they run dry.)
Trekking poles if you use them.
Sunscreen: most of this hike is unshaded.
A windbreaker: it gets very blustery at the top.
Layers: you'll sweat all the way up, so you could catch a chill on the way down.
A first-aid kit with blister treatment: the hard, dry miles can do a number on your feet.
Snacks to replenish your energy supply.