Some hours up Hwy 1 you can find Fort Ross, a remnant of Russian presence in California.
With its old craft tools and armory it is well worth the trip and the surrounding nature - a bluff with a chance to see abalone mussels and enjoy the tide pools - makes it very easy to spend many hours here.
Apart from the well preserved remnants of the buildings and palisades, the museum has an adjoining building with an exhibition explaining the history.
The ford is located north of Russian River where there are many other opportunities to enjoy nature, beach, seals, kayaks, and to find a place for the night. Alternatively, one can settle down in Bodega Bay, another resort spot where Hitchcock filmed the thriller "Birds" a lifetime ago.
This part of Sonoma County between 101 and Hwy 1 holds many vineyards less known than the Napa and Sonoma Vallies but much is cattle land. A trip out to Point Reyes can be combined with a trip up here.