Sebastiani Vineyards & Winery is one of Sonoma's historic names, close enough to the plaza that you can fold it into a town visit without turning the day into a driving loop. Its long local presence gives it more weight than a generic tasting room.
The experience is still a tasting, so the usual wine-country cautions apply: book ahead when needed, pace yourself, and do not try to turn every stop into a checklist. Sebastiani works best as a grounded, old-Sonoma counterpoint to the valley's newer and more design-heavy wineries.