This is the first of three houses built for and bearing the name of Harrison Gray Otis, Boston's third mayor and a prominent citizen and developer. It's now the headquarters for the Society for the Preservation of New England Antiquities (SPNEA), an organization that owns and maintains dozens of properties throughout the region. The society restored the 1796 house; two of the floors are open as a museum. The furnishings, textiles, wall coverings, and even the interior paint, specially mixed to match old samples, are faithful to the Federal period, circa 1790-1810. You may be surprised to see the bright and vivid colors favored in those days. The dining room is set up as though Harry Otis were about to come in and pour a glass of Madeira. But Otis lived here only four years before moving to more-sumptuous digs, designed by Charles Bulfinch, on Beacon Hill. A corner of the museum details the house's history after Otis moved out. A second-floor room brings to life the home's days as a late-19th-century boardinghouse, and a hallway display describes the "champoo baths" of former resident Mrs. Mott. Thought a quack in her time, she actually promoted the first aromatherapy saunas. A summertime Beacon Hill walking tour originates here.