Any good Northern California clothing-required hot springs / public baths?

My mom always goes up to Calistoga up in Napa Valley.

I second Calistoga. There are lots of choices, charming places to stay, and wineries too.

Any specific places in Calistoga? I spent time there years ago, and the places I went are now closed. Any specific hot spring or spa (hopefully not just a massage/facials/etc place but with hot baths, sauna, steam, etc) ?

It has been too many years for me to make a personal recommendation (same as you). Indian Springs has a good review. Excerpt: “This spa has the best mud bath in Calistoga. I have tried others, but this one takes the cake. For one thing they use the volcanic ash and water to make a thick mud using the geyeser mineral water. They do not add peat moss as do the others. The mud sticks to you much better this way.”

Fodor’s, whom I usually find trustworthy, lists these.

Have a great time.