A recent favorite hiking path in Mount Diablo State Park (in Northern California) to North Peak is considered the hard way. You'll have over 3,000 feet of climbing on some of the toughest ascents in the region in the first five miles. Do know that you're going from sea level to this new altitude, yet you are truly rewarded for the effort.
This is NOT an easy hike. Have food, water, layers and be prepared for the uphills. Well worth the effort on the way up! Enjoy this 10 + mile hike that gives you the very best of the East Bay views and miles.