Ancient Roman baths and a 15th-century mansion set the stage for a terrific collection of Medieval art and objects at this museum. Built somewhere between the 1st and 3rd centuries, the baths (visible from bd. St-Michel) are some of the best existing examples of Gallo-Roman architecture. They are attached to what was once the palatial home of a 15th-century abbot, whose last owner, a certain Alexandre du Sommerard, amassed a vast array of Medieval masterworks. When he died in 1842, his home was turned into a museum and his collection put on display. Sculptures, textiles, furniture, and ceramics are on display, as well as gold, ivory, and enamel work. Of the several magnificent tapestries the biggest draw is the late-15th-century Lady and the Unicorn series, one of only two sets of complete unicorn tapestries in the world (the other is in New York City).

Among the many sculptures displayed are the famous severed heads from the facade of Notre-Dame. Knocked off their bodies during the furor of the Revolution, 21 of the heads of the Kings of Judah were found by chance in 1977 during repair work in the basement of a bank. Other treasures include Flemish retables, Visigoth crowns, bejeweled chalices, wood carvings, stained-glass windows, and beautiful objects from daily life, like hair combs and game boards.