This is in the outside portion of the Caracalla spa, one of the two large public "Thermes." The Caracalla is the larger and livelier of the two, like a healthful waterpark. Several pools of varying sizes, temperatures, and depths; steam rooms with eucalyptus-infused steam and twinkling lights on the ceiling, a mini "river" complete with natural feeling current; "aroma-saunas," and an experimental "blue room" with pulsating chairs, blue lights, and ambient music. We came here as soon as we got in (after driving almost 7 hours) and left 3 hours later feeling relaxed with legs like mashed potatoes :)