Thermae be applied to those magnificent edifices which grew up under the empire, in place of the simple balneae of the republic, and which comprised within their range of buildings all the appurtenances belonging to the Greek gymnasia, as well as a regular establishment appropriated for bathing. Writers, however, use these terms without distinction. Thus the baths erected by Claudius Etruscus, the freedman of the Emperor Claudius, are styled by Statius "balnea", and by Martial "Etrusci thermulae". In an epigram by "Martial"—"subice balneum thermis"—the terms are not applied to the whole building, but to two different chambers in the same edifice.
Ancient Roman architecture air. The Roman architect Vitruvius, writing about the end of the 1st century B.C., attributes their invention to Sergius Orata. Many remains of Roman hypocausts have survived throughout Europe, western Asia, and northern Africa. The hypocaust was an invention which improved the hygiene and living conditions of citizens, and was a forerunner of modern central heating. Hypocausts were used for heating hot baths (thermae), houses and other buildings, whether public or private. The floor was raised above the ground by pillars, called pilae stacks, with a layer of tiles, then a layer of concrete, then another of tiles on top;