Di Rosa Preserve in Napa (well, just outside of Napa) is a great place to spend a few hours. There is a gallery which is free to the public. All modern art.
But take the two hour tour for $16 (as of this writing). A shuttle takes you through the grounds. There are outdoor sculptures and peacocks. There is a huge gallery. All the art is modern, and I recall that it is mainly Bay Area artists. The tour concludes in the house, which is something to see. I can just imagine the "parties" that must have gone on in that house.
Small gift shop with some reasonably priced souvenirs and practical items.
We all had a good time and would recommend this, especially as something different from wine tasting.
This review is the subjective opinion of a TripAdvisor member and not of TripAdvisor LLC