The huge rectangular area occupied by the Baths, erected between 298 and 306 A.D., is of approximately 140,000sqm, excluding the tanks, discovered in Piazza dei Cinquecento, fed by the water of the aqueduct of the Aqua Marcia. Built in brick stone, the baths could accommodate up to 3000 people simultaneously. The huge thermal complex housed a central building with calidarium, tepidarium and natatio (rooms for hot or warm baths and swimming pools filled with cold water, partly preserved) disposed along the short axis, and gymnasiums on both sides of the long axis, with a large court all around used as garden.