A luxe tub surrounded by flowing curtains is part of Spa Solage's modern take on the soaking portion of the Calistoga bathing circuit.

For centuries, Calistoga, CA, has been a mecca for geothermal healing enthusiasts. Native Americans gathered there to detoxify and purify in the area's steaming pools and rivers, which are rich in magnesium and calcium. Later, in the 1850s, California millionaire Sam Brannan purchased 3,000 acres there and made it his mission to create a healing haven comparable to New York's famed Saratoga Hot Springs. He opened up the Hot Springs Hotel in 1860 as a place where guests could immerse themselves in the hot mineral water and slather their bodies with a mud concoction he created by mixing volcanic ash from nearby Mount St. Helena with the water. This mixture helped establish the region's famed tradition of mud baths, which are said to detoxify, relieve injured muscles, and help soothe stiff joints. Since that time, Calistoga, which is nestled in the wine-laden heart of Napa Valley, has become an acclaimed resort town that is a magnet for those who come to partake in the healing spa circuit that combines immersion in mud and water followed by a period of rest. With the opening of Solage Calistoga, an 89-room contemporary resort that is home to Spa Solage, that tradition is getting an exciting update and turning the new property and spa into the toast of the town. "What sets it apart from other spas in Calistoga is that the mud experience is totally new," says spa director Peggy Francis. "We've just taken the old Calistoga experience and put a twist on it."

The mud option, dubbed the Mudslide ($95, 60 minutes), at the spa's Bathhouse begins when spa-goers sidle up to the Mud Bar, where Mudtenders create a mix of Solage Mud, essential oils, geothermal water, and an antioxidant-rich signature serum filled with grapeseed, green tea, pomegranate, strawberry, and wasabi root extracts. Guests can choose from an invigorating Mud Mojito, a relaxing Lavender Mudtini, a sensual Mud Mimosa, or the Sam Brannan Muscle Soother, which is loaded with essential oils that relieve aching muscles. They can also sip on an indulgent elixir or a low-alcohol mini-cocktail. Next, guests paint themselves—or each other if they are there with a group or as part of a couple—bypassing the traditional dip in a communal tub full of mud. "The benefits of this, and the reason it is great to apply it to yourself, is that you really want to get it into the areas where your lymph nodes are, which is in the groin, chest, and under the arms," explains Francis. "Then the mud holds these great essential oils and serum on the body, so it's a very detoxifying program."

Prior to the Mudslide, guests sidle up to the Mud Bar to select their signature Mud-tini.

After the mud application, guests then enter either the heated group Mud Lounge or the private Couples' Lounge and allow the mixture to dry for approximately 20 minutes. An attendant then instructs guests to rinse off and guides them to the bathtub room. There, they soak in warm geothermal water in a modern-style bathtub that is inspired by iconic Calistoga clawfoot tubs for 15 more minutes while enjoying a cold drink and a cool compress for the head. The "rest" portion of the experience is next. However, in lieu of taking a catnap on a cot, guests get a space-age spot to chill out in one of five SO Sound Chairs, which hold the body at a zero-gravity position and pump soothing music through headphones and the chair, providing them with vibrational healing therapy. Finally, guests can enter either one of three heated mineral pools—a co-ed pool and separate men's and women's pools—as well as cold plunge pools and a steam room. "The Mudslide is very popular, and I think it will gain more popularity as people begin to understand the detoxification process," says Francis.