The Terme di Diocleziano was ancient Rome's largest bath complex, covering about 13 hectares and able to accommodate some 3000 people. Today its ruins house a branch of the impressive Museo Nazionale Romano. Exhibits, which include memorial inscriptions, bas-reliefs and archaeological artefacts, provide a fascinating insight into Roman life. Outside, the vast cloister, constructed from drawings by Michelangelo, is lined with classical sarcophagi, headless statues and huge sculpted animal heads, thought to have come from the Foro di Traiano.
Elsewhere in the museum, look out for exhibits relating to cults and the early development of Christianity and Judaism. There's a particularly interesting section about amulets and spells, which were cast on neighbours and acquaintances to bring them bad luck and worse. Upstairs you'll find tomb objects dating from the 11th to 9th centuries BC, including jewellery and amphorae.
As you wander around the museum, you'll see glimpses of the original complex, which was completed in the early 4th century as a state-of-the-art combination of baths, libraries, concert halls and gardens – the Aula Ottagona and Basilica di Santa Maria degli Angeli buildings were also once part of this enormous endeavour. It fell into disrepair after the aqueduct that fed the baths was destroyed by invaders in about AD 536.
Note that the museum is one of four that collectively make up the Museo Nazionale Romano. A combined ticket, which is valid for three days, includes admission to the other three sites: Palazzo Massimo alle Terme, Palazzo Altemps and the Crypta Balbi.