The baths consisted of a central frigidarium (cold room) measuring 58 by 24 m (190 by 79 ft) under three groin vaults 32.9 m (108 ft) high, a double pool tepidarium (medium), and a circular caldarium (hot room) 35 m (115 ft) in diameter, as well as two palaestras (gyms where wrestling and boxing were practiced). The northeastern end of the bath building contained a natatio or swimming pool. The caldarium had seven pools, the frigidarium four, the tepidarium two. Next to the caldarium were saunas (laconica). The Baths of Caracalla were the city's second largest Roman public baths, built between AD 212 (or 211) and 216/217, during the reigns of emperors Septimius Severus and Caracalla. The baths were in use until the 530s. The art works recovered from the ruins include famous sculptures such as the Farnese Bull and the Farnese Hercules. The bath main building was 214 x 110 meters and the height to the top of the roof line was 44 meters (145 ft.); it covered 6.5 acres and could hold an estimated 1,600 bathers.