California - Things to do in Napa on a Saturday afternoon

My husband and I will be traveling to Napa (Yountville) for a conference of his in early May. Friday and Saturday evening are booked with dinners and wine tastings, but I've got Saturday afternoon to tool around on my own while he's doing his conference stuff. Any suggestions on stuff to do?

Also, how big of a pain would it be to drive to the Nevada City/Grass Valley area from Yountville? We have some relatives up there that I could call if there wasn't enough to occupy myself with locally. TIA

Grass Valley's at least 2 hours away. You probably wouldn't want to do it as a half-day trip.

As for things closer to Yountville:

Wineries generally close at 4-5. If you're only doing evening tastings on Friday and Saturday, you'll miss the chance at winery tours. If you haven't toured a winery before, one excellent tour is Domaine Chandon, right in Yountville. They also have lovely grounds for spending an extra hour or two. Another great tour is at Robert Mondavi, a bit up the road in Rutherford.

If you like the outdoors and aren't particularly interested in enjoying a winery's grounds (frankly they're much more interesting with a glass in hand) visit one of the many parks in the area.

If you're more of a spa person, consider a mineral bath or mud bath in Calistoga.

Or, finally, just sit around the hotel room with your Internet connection and read FlyerTalk, like I do.

Along the outdoors theme, you could rent a bike and go for a ride. Can be combined with wine tasting if you haven't had enough yet... just stay off Hwy 29 and watch out for cars.

Wow - if I had "free time" I would head to Calistoga and spend the afternoon here:

http://www.indianspringscalistoga.com/spa/#

If you have never done a mud bath - you are missing pure bliss and Indian Springs is lovely.