Nothing rejuvenates Bay seniors like a soak in a 5 million year old hot springs. This one, Vichy Springs up in Ukiah, is also the only warm-water, naturally carbonated mineral bath in North America. It’s what attracted weary, creaking geezers like Mark Twain and Teddy Roosevelt to stop in for an ablution. This 150 year old resort is located on 700 acres of rolling open space, including an easy trail to the splendid, 40-foot high Chemisal Waterfall. Rooms start at $195 per couple. A day pass to the baths and the trails is $50.