The National Roman Museum – Octagonal Hall (ex Planetarium) was created in the halls of the ancient Thermae of Diocletian and exhibits an important number of sculptures, all coming from thermal complexes. 

It also contains works that came to light during the excavation works performed in Rome and in its surroundings, such as the Venus of Cyrene or the Girl from Antium, realized by Greek sculptors of the fifth century BC. Inside the building the visitor can admire frescoes of the Republican Age.