From SF, take I-80 to Sacramento Then I-5 North to the HWY 99/70 exit (to Marysville/Yuba City)Rt. exit! Follow HWY 99 north to HWY 70 exit (Rt.) Proceed north through Marysville and then Oroville Continue on 70 past Oroville up the Feather River Canyon. This is where the drive is very beautiful! There are a couple cool tunnels to drive through on the way up! The Spring is near the "very" small town of Twain, and is marked on most maps. If you get to the HWY 89 exit, you passed it! It is a nice stone work tub with a main area and a smaller connected tub. It will be on your Rt. heading up the road. Park in the lot near a mobile home park rt off the roads edge. There is a place to put a dollar (1$ per person), and follow the trail to the tub! A short easy walk! Best times for solitude are mid week and early am or evenings. It's a popular spot but I've had it to myself many times. I have also enjoyed the folks I've met there, never any problems! It is clothing optional.