Baths of Caracalla , Rome, Italy

The Baths of Caracalla (Thermae Antoninianae) were built between a.d. 212 and 216 by the emperor Marcus Aurelius Antoninus (a.d. 188–217), usually known as Caracalla. Although in layout the Baths of Caracalla largely emulated the model established about a century before in the Baths of Trajan, their massive scale and opulent internal finishes were without precedent. Their fully integrated plan and imposing scale and grandeur amply demonstrated the Romans’ design skills. Significantly, the baths demonstrated the structural advances made possible through the masterful use of concrete to span vast spaces using barrel and groin vaults, domes, and half-domes, as well as the sophisticated mechanical engineering services developed by the Romans.

Public baths (thermae) were an essential part of all Roman towns. The majority of citizens lived in crowded tenements (insulae) without running water or sanitary facilities, so communal baths were constructed and made available to both sexes of all social classes. Entry was free. Generally, mixed bathing was not favored, so the baths were open to women in the mornings and men in the afternoons and evenings. The thermae were the center of Roman social life—people could meet friends there and engage in any number of leisure and cultural pursuits on offer. As well as changing rooms, gymnasia, saunas, and pools of various temperatures, there were libraries, museums, restaurants, bars, shops, lecture theaters, concert halls, playing fields, gardens, and courtyards, all richly furnished with mosaics, fountains, and statues. Although extremely costly to build, the baths were a political investment—a means for the emperor to demonstrate his concern for the well-being of the community.

The Baths of Caracalla occupied a 50-acre (20.25-hectare) site. The complex was divided into three parts: the rectangular main building, approximately 750 by 380 feet (225 by 115 meters) and large enough to accommodate 1,600 bathers; encircling landscaped parks and gardens; and a perimeter ring of shops, lecture halls, and pavilions. Laid out symmetrically, the compactly planned baths offered identical bathing circuits on either side of the central (and shorter) axis. The sequence of bathing spaces on that axis comprised the hot bath (caldarium), warm bath (tepidarium), and the cold bath (frigidarium) in a large unheated central hall. The last, which also served as a foyer, was open on one side, allowing easy access to the open-air swimming pool (natatio). Changing rooms (apodyteria), gymnasia, or exercise yards (palaestrae), with terraced porticoes, and sauna (laconica) were arranged symmetrically on the transverse axis. Rooms for massage, manicure, and other services associated with the bathing routine were featured on either side of the baths. Decorative interior finishes—colored marble veneers on walls, marble, basalt and granite columns and arches, and coarsely textured black-and-white mosaic floors—created a rich and sumptuous character.

Since the baths were public facilities that attracted large numbers of people, the gathering spaces needed to be vast and uncluttered with structural elements. In the absence of structural impediments, bathers were afforded extended views to various parts of the thermae. The Romans achieved these objectives by exploiting the semicircular arch. The rectangular central hall of the Baths of Caracalla demonstrated their structural method. It was roofed with an enormous semicircular intersecting concrete vault divided into three compartments. Each was 108 feet (30 meters) high and rested at the corners on enormous piers. Clerestory windows adequately lit the hall.

Water for the Baths of Caracalla flowed from a branch of the Aqua Marcia aqueduct into a huge reservoir, divided into eighteen chambers with a total capacity of about 2.2 million gallons (10 million liters). The water was carried through pipes laid underneath the gardens to the main building, where it was distributed directly to the cold pools, or to wood-fired boilers, where it was heated for the warm and hot baths. For ease of inspection and maintenance, distribution pipes and waste drains were located in separate tunnels. A separate network of tunnels was used to store wood for about fifty furnaces (praefurnia) that heated the saunas (laconica) and other rooms via a hot-air system (hypocausta) beneath the floors. The heated rooms were on the southwestern side of the complex to gain maximum benefit from the sun; all had large windows. The hottest room, the circular, protruding caldarium, was covered by a 115-foot-diameter (35-meter) dome, higher than the Pantheon’s and only slightly less in span.

The Baths of Caracalla are now in ruins, but their soaring height and impressive scale allow visitors to appreciate their size and massiveness.