Many of the Mill Valley homes are situated at the base of, or crawling up Mount Tamalpais, though of course there are homes in the valleys, themselves. An interesting point of fact is that streets for the hill homes are almost all very old, very narrow and filled with pot-holes. Funny, as the cost of a CHEAP house in Mill Valley (i.e. one that needs to be torn down and then you can rebuild on the lot) would easily cost you $500,000us (if not more). Expensive real estate with terrible roads. I don't know. I'm fond of it, since I've grown up with it. But look at the views of a median-priced home.
One of my favorite walks. This is within the first half mile, where it's paved (for emergency vehicles). Not much farther towards the beach, the road becomes a trail. The trail ends at Tennessee Valley Beach, which is beautiful and wild and not somewhere you'd go swimming unless you had a death wish.
This path was a favorite of my granny's, so we walked it together from time to time.