Solage, Auberge Resorts Collection

Solage sits in Calistoga at the northern tip of Napa Valley, where the volcanic geology that produces world-famous wine also generates natural hot springs that have drawn visitors since the 19th century. The Solage Spa's signature is the Mudslide — a circuit of geothermal mud bath, mineral pool, and sauna that follows the natural hot spring tradition Calistoga was built upon — alongside contemporary outdoor barrel saunas installed facing the vineyards. The property covers 22 acres of Northern California wine country, and its 89 bungalow-style studios blend Napa aesthetics with a spa philosophy that takes the geothermal landscape seriously. Solage has consistently ranked among America's top ten destination spas.