There is a trail that runs right behind my apartment complex, and when the weather is nice or I am in the mood for a little exercise, I head straight to it. It's called "The Napa River Trail" and it was originally planned to run a long length of the Napa River, from the north end here at Trancas (you can pick up the trail off of Trancas near the intersection with Silverado Trail) all the way south to Vallejo. Obviously, that would be a huge undertaking and with the state of the state and local budgets, it hasn't been done. However, bits and pieces of the trail have been made, and one of them is here, running along the riverside for 1.1 miles between Trancas to the north and Lincoln to the south.
If you're ever in the area, or taking a bike ride through Napa, this can be a nice and leisurely little diversion -- despite running right behind homes and apartments, the trail is quite quiet and tranquil, populated by a variety of people seeking such asylum including families, dog-walkers, joggers, and even a few folks who head to the river bank for some leisurely fishing. At the southern end near Lincoln, there is also a complex of time-shares and tiny vacation cottages which can be rented, each their own self-contained unit with little decks, grills, and tables to enjoy a meal right next to the trickling stream (which is usually more like a creek at this part of the river).