Named for California’s northernmost mission of the 21 founded by Franciscan monks from Spain, which lies 2.5 miles south, this grande dame of Wine Country hotels was built in 1927 on the site of an earlier hot springs resort. In more recent years, it’s been renowned for its 40,000-square-foot, European-style Willow Stream Spa, including 30 treatment rooms, three mineral water baths, Watsu pool and a custom “rain tunnel.” Spa users have exclusive access to the outdoor geothermal pool, whose source spring contains 27 different minerals. Explore the gorgeous surroundings on a free, docent-led hike at 9 am Friday through Sunday.