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.
Thermae Romae story follows a Roman architect named Lucius, who is having trouble coming up with ideas. One day, he discovers a hidden tunnel underneath a spa that leads him to a modern Japanese bath house. Inspired by the innovations found there, he creates his own spa, Roma Thermae, bringing in the modern ideas to his time. Each subsequent chapter follows Lucius facing some sort of a problem, just to be swept to Japan once again. He visits modern bath houses, personal baths, waterparks, fertility festivals, and even zoos. There, he always happens to find the inspiration to solve the exact problem