Favorite thing: Calistoga is also the home of the Calistoga Mineral Water Company. In Northern California, you will find sparkling Calistoga water all over the place. It's almost as pervasive as wine. Instead of saying "I'll have one of them Co-colers", the locals here ask for "one of them Calistogas". Non-purists (the same types who would order a guava margarita or a pumpkin cheesecake) buy some of those flavored waters, but I've always thought the original non-flavored sparkling water is best. The sparkling mineral water does really come out of the ground in its sparkling state. The bottling plant was built around a geyser, and the geyser water now ends up on your table. Calistoga Mineral Water Company is now owned by a mega-corp., Nestle, but it still is good.
Favorite thing: We went to Calistoga Spa Hot Springs and soaked in their giant octagonal jet pool, then swam in the mineral pool. It was very relaxing, we had a day pass so we left and ate lunch and shopped, wine tasted and then came back and swam again.