In the 1800s, the big draw in this region wasn’t wine, but hot mud baths. The Quake of 1906 shifted the location of many of the springs, wiping out most of the wells that then existed in Sonoma County as well, so that today, the best place to participate in a geothermal treatment is in Calistoga in Napa County. Like bungee jumping or hot-air ballooning, it’s a once-in-a-lifetime vacation treat

Most places mix the mud and hot springs water (which is a little over 100 degrees) with clay, peat, and volcanic ash from nearby St. Helena volcano, which may stain some swimsuits, so don’t wear your best one, or, like most people, don’t wear anything at all. These treatments used to be touted as an excellent treatment for arthritis, but modern marketing laws being what they are, they’re now meant mostly as stress relievers (though supporting scientific studies show that arthritis suffers may, in fact, find some relief).

The following day spas all include mud baths—the most “local” of the treatment—and other treatments such as massage and hydrotherapy (check their websites for full menus). Some mud baths are thick, others soupy; some start as mineral-water baths before having ash mixed in (to prove it’s fresh, I suppose), and others offer a pre-mixed tub before you begin. The style doesn’t matter but make sure the spa you visit uses mineral water, which means it’s been drawn hot from the earth.

  • Dr. Wilkinson’s Hot Springs Resort (1507 Lincoln Ave., Calistoga; tel. 707/942-4102; www.drwilkinson.com), set in a delightfully 1950s motel complex, has been a player in Calistoga for generations and offers a range of treatments, but it’s basic in the classically medicinal sense that spas once had. The mud bath as described above is $89 and takes a little over an hour.
  • Golden Haven (1713 Lake St., Calistoga; tel. 707/942-8000; www.goldenhaven.com), with its couples-sized tubs, is popular with honeymooners. A treatment costs $89 per person ($72 Mon–Thurs in winter).

Note: This information was accurate when it was published, but can change without notice. Please be sure to confirm all rates and details directly with the companies in question before planning your trip.