The Diocletian Baths include the National Roman Museum (or rather, one of the four locations, together with Palazzo Massimo, Palazzo Altemps and Crypta Balbi).
The plant of the Diocletian Baths is the oldest in Rome (it was in fact built between 298 and 306 AD. In the building, where there are the classic pools of water with different temperatures (calidarium, tepidarium and frigidarium) it also had an outdoor pool called natatio and a central basilica hall.
Part of the perimeter of the baths, today, is occupied by the church of Santa Maria degli Angeli, since Pio IV in 1561 wanted to transform the baths into a basilica with a convent.
