public baths in ancient Rome that served also as social, entertainment, and sports centers. The thermae had assumed their basic architectural form by the second century B.C., during the republican period, and became fully developed under the empire. Most consisted of an intricate complex of buildings, each of which was divided into numerous chambers. The main building usually followed a symmetrical plan. The frigidarium (cold room), tepidarium (warm room), and calidarium (hot room) were placed along the building’s major axis and were flanked on either side by a vestibule, a dressing room, bathing rooms, rooms for massage, and steam rooms. There was also an exercise court. (Some provincial thermae, in contrast, lacked this symmetrical scheme.)
The immense inner rooms featured domes and huge barrel or groin vaults; the main building, for example, of the Baths of Car-acalla in Rome (early third century A.D.) measured 216 m by 112 m and had a dome 35 m in diameter. The inner rooms were lavishly adorned with mosaic, paintings, sculpture, and other works of art.
The thermae were heated with hot air that circulated in conduits usually built under the floors or in the walls. Often water from hot springs was used. There were also private thermae.