Back in the spring of 2014, Relais & Châteaux’s Castle Hill Inn, an 1875 Victorian mansion on Narragansett Bay, teamed up with herbal skincare brand Farmaesthetics, also based in Rhode Island, to offer facials, massages, and therapeutic treatments for three months. “Once we popped up, we all knew instantly that this was a natural fit,” says Farmaesthetics founder and CEO Brenda Brock. The inn had given up two of its nine coveted guest rooms, with fireplaces and bay views, to create the Retreat at Castle Hill by Farmaesthetics, and this summer it debuted a relaxation area outside the treatment rooms, making the intimate spa a permanent installation. We found the brand’s all-natural emollients intoxicating, especially the two-and-a-half-hour Rose Immersion treatment ($375), which Brock developed exclusively for the inn. The experience begins with a hot sea salt bath to soften skin, followed by a tension-relieving rose essential oil massage, and ends with a deep-cleansing facial incorporating the Vassar Rose Perfecting Polish, Farmaesthetics’s natural alternative to microdermabrasion. With an herbal hydration complex, nourishing oil, and serum, the facial is as calming as the privacy of the suite. Treatments from $125; rooms from $795; 590 Ocean Dr.; 401-849-3800; castlehillinn.com.