SONOMA MOUNTAIN REGIONAL PARK
From 2005 to 2012 agencies worked to piece together various land trust properties and created the 820 acre North Sonoma Mountain R.P. To date, it includes a nice 4 mile round trip hike that goes from about 1050' through open grasslands and oak woodlands to about 1750' for a panoramic view of the valley. A
second 1.5 mile round trip hike, the Umbrella Tree trail, heads up a steep 450 foot climb to yet another viewpoint. The park has a unique entrance across a small bridge and up a narrow one way road to a very bucolic parking lot and trailhead.
Map location: here
Trailhead picture/info here.
Park trail map here.