(Above and below image from http://www.drwilkinson.com).
I love spa treatments, and over the course of my life I've done a lot of unusual ones: Aromatherapy "color baths" with light lasers, a gong bath, cupping, a facial with a "tesla wand," high-end seaweed wrap, no-touch reiki massage, etc. But immersing in a 4-foot tub of volcanic-ash mud last week in Calistoga, CA was by far the oddest treatment I've ever undergone. Dr. Wilkinson's has been around for over 60 years, and the retro look and feel of the buildings and locker rooms doesn't hide this fact.
Here's the procedure: You lock up your things, grab a bathrobe and are escorted by attendants (of your gender) into a large tiled room that has two large, rectangular tiled baths, mounted a few feet above floor level. They're filled with sulfuric-smelling "volcanic-ash" mud. THIS IS NOT FOR THE SQUEAMISH. You strip down and the attendants assist you into the oozing, bubbling, stinky tubs, while reciting some science-y factoids to try and convince you that this is not the most disgusting thing that has ever happened to you.
Sinking into the mud is not as easy as it sounds: It's very thick (and did I mention BUBBLING), and it takes about a minute to get yourself fully immersed, up to your neck. If you're me, this is where some mild panic sets in, (AS THE MUD SINKS INTO EVERY CORNER OF YOUR BODY). Your attendant then gives you a pillow to rest your head on, and places cucumbers over your eyes, and instructs you to relax for ten minutes (easy for her to say). Once the time is up, you are escorted out of the tub and proceed to take the most complete shower of your life. Next is the wet-sauna (the attedants hand you glasses of cucumber water through a little window), for another ten minutes. Then, you head to an old-fashioned clawfoot bathtub behind a curtain (in the same room), which is being pumped full of hot-spring water. Last, the attendants have you shower one last time, and lead you to a relaxation cube, where you're wrapped loosely in towels for ten more minutes, while your body temperature returns to normal.
You can't take pics inside the spa of course, but my pal and I stayed in one of the cottages Dr. Wilkinson offers, and hit the outdoor tub later that night. And if you're curious about what the tubs look like, you can see images here.