Like all great Roman cities, Aquileia also had its thermal baths. The complex of the Grandi Terme, only partially known, and today investigated by the University of Udine, has been brought to light since the beginning of the twentieth century.

They extended over an alleged area of two and a half hectares. So far, the hot baths, cold baths and classrooms-gym sectors have been highlighted, decorated with sumptuous mosaic floors (some of which are currently on display at the National Archaeological Museum).

Thanks to an inscription, we can trace the name of the large building: Terme Felici Costantiniane. It is connected to the figure of Constantine the Great and dates back to the first half of the 4th century. The plan is comparable with that of the Baths of Constantine in Rome, on the Quirinale, which were probably the reference model for the design of the Aquileia complex.