You can fill several days here without a wine glass — an art park, a redwood grove, Jack London's ranch — and the wine-adjacent attractions are worth booking well ahead because most now run by reservation only.
Napa Valley Wine Train
Departs from 1275 McKinstry Street in Napa on restored carriages, with trips from about 2.5 hours for the murder-mystery dinner up to a six-hour Legacy run with winery stops; the standard lunch and tasting services are around three hours. Book through the operator, and expect it to be the single biggest line item of the trip.
Castello di Amorosa
A full-scale Tuscan-style castle winery at 4045 St Helena Hwy in Calistoga, built with traditional medieval techniques rather than as a facade. Open daily 10am to 5:30pm by reservation only, with tour-and-tasting packages; the wines are sold only on site and through the winery.
di Rosa Center for Contemporary Art
A 217-acre art park in the Carneros district south of Napa holding more than 1,600 works by Northern California artists, shown across galleries and outdoors on the grounds. Programming includes rotating exhibitions and guided hikes; check the site for current opening days before driving out, as it does not open daily.
Jack London State Historic Park
2400 London Ranch Road in Glen Ellen: the writer's Beauty Ranch, the ruins of Wolf House, his cottage and grave, and the House of Happy Walls museum, plus hiking, mountain biking and horse trails across the property. Hours and the vehicle fee are on the park's directions page; passes can be bought online in advance.
Armstrong Redwoods State Natural Reserve
Old-growth coast redwoods three miles north of Guerneville on Armstrong Woods Road, open 8am to an hour after sunset for $10 per vehicle, $9 for seniors. The Colonel Armstrong Tree, reckoned to be over 1,400 years old, is an easy half-mile walk from the entrance, so it works even with a short afternoon.