Mount St. Helena (Robert Louis Stevenson State Park)

Wine country's loftiest summit, rising 4,343 ft at the county's northern edge. The classic out-and-back to the top runs about 10 miles round trip with some 2,000 ft of climbing — a half-day workout on shaded switchbacks and open fire road, rewarded with views that reach Mount Shasta and the Sierra on the clearest days.