Named for the emperor Caracalla, the baths were completed in a.d. 217, after Caracalla’s death. The richness of decoration has faded, and the lushness can be judged only from the shell of brick ruins that remain. In their heyday, they sprawled across 11 hectares (27 acres) and could handle 1,600 bathers at one time. Partially opened to the public in 2012, the tunnels below the complex give an idea of the scale of the hydraulic and heating systems that must have been needed to serve 8,000 or so Romans per day.

The palestra (gym) is one setting for summertime outdoor operatic performances in Rome.