U.S. wine producer Robert Mondavi is the most globally famous in Napa Valley. If you only make one stop in the valley during your visit, this is the place to go. Be aware that tastings are quite pricey! A little further down Highway 29, you can find the area of Opus One, where you can go for a nice walk and see lovely views of the vineyards.
In Napa Valley it's essential to make at least one visit to a winery. The one we chose was this, for the sparkling wine ... you know. We were not disappointed. A well maintained building with beautiful gardens and an indoor area large enough for tasting and very atmospheric. The prices of both the tasting and the products that are for sale, are reasonable. What I like are the outdoor table that are in a lovely setting.