Bonsai trees, bamboo gardens, and trickling streams cover the five secluded acres that make up Osmosis Day Spa Sanctuary, which brings a relaxing piece of Japan to Northern California. But this escape from the modern world doesn't just surround its visitors with nature—it literarily immerses them in it, thanks to the Cedar Enzyme Bath.

Osmosis founder Michael Stusser discovered the treatment in Japan, and he made it his spa's signature service upon opening in 1985. The experience begins in the tea garden, where 25 organic plants lend their benefits to a hot herbal tea. Things then move inside, where guests dip down into wooden tubs filled with finely ground cedar, rice bran, and plant enzymes imported from Japan—which create a natural warmth through fermentation. The warmth relaxes the entire body, and proponents believe it has numerous health benefits. After they're warmed through and pleasantly cozy, guests can explore the plants and water features out in the meditation garden, or stay inside for different spa treatments, from facials to massages.