Aula Ottagona

The Aula Ottagona, or Octagonal Hall, is probably the best surviving structure from the Baths of Diocletian. Built in 306AD, the baths were the largest of the ancient world and could hold up to 3,000 people at a time.

History of Aula Ottagona

Once the largest ancient baths complex in the world, the Baths of Diocletian – or Terme di Diocleziano – was built between 298AD and 306AD in honour of the Roman Emperor Diocletian. Today, they are open to the public as part of the National Roman Museum in Rome, Italy.

The Aula Ottagona (Octagonal Hall), more commonly known as the Planetarium, has reopened. It is located in the western corner of the Baths of Diocletian and is of a square plan outside with an octagonal interior. The roof, which consists of a dome with eight ribs, was originally decorated with figured marbles and stuccoes which have now disappeared.

Its location between the calidarium (the hot plunge bath room) and the gymnasium and its lack of heating system has led to the assumption that the room served as a minor frigidarium (cold plunge room) for ablutions.

The hall has been remodelled and used for different purposes since 1878, when, along with the opening of the via Cernaia, it was isolated from the main complex. It was first used as a seat for the Gymnastics School, then as a room for Minerva film projections, then finally in 1928 it was the seat of the largest Planetarium in Europe.

Aula Ottagona Today

Today, the remains of the baths can be seen over a wide area, with parts of the structure having been incorporated into other buildings, such as the Basilica Santa Maria degli Angeli e dei Martiri.

Today, a series of bronze and marble statues from the Baths of Diocletian and Caracalla are exhibited within Aula Ottagona as part of the National Roman Museum. These statues are copies of statues of Greek art which represent divinities, athletes and heroes, and are evidence of the masterpieces that once adorned the great Roman baths from the 2nd-4th centuries AD.

It is worth looking out for temporary exhibitions which are sometimes held at the site.

Other areas of the Baths of Diocletian can also be explored in the nearby Basilica Santa Maria degli Angeli e dei Martiri and Church of San Bernardo alle Terme.

Getting to Aula Ottagona

From the centre of Rome, the baths are reachable in around 5 minutes via the Viale Luigi Einaudi and Viale Enrico de Nicola roads. By car, the baths take around the same amount of time via the same route. There is also an extensive public transport system for those travelling to see the baths from different parts of the city.