TEPIDARIUM, the term given to the warm (tepidus) bathroom of the Roman baths. There is an interesting example at Pompeii; this was covered with a semicircular barrel vault, decorated with reliefs in stucco, and round the room a series of square recesses or niches divided from one another by Telamones. The tepidarium in the Roman thermae was the great central hall round which all the other halls were grouped, and which gave the key to the plans of the thermae: it was probably the hall where the bathers first assembled prior to taking the cold bath or passing through the various hot baths, and was decorated with the richest marbles and mosaics: it received its light through clerestory windows, on the sides, the front and the rear, and would seem to have been the hall in which the finest treasures of art were placed; thus in the thermae of Caracalla, the Farnese Hercules, and the Toro Farnese, the two gladiators, the sarcophagi of green basalt now in the Vatican, and numerous other treasures, were found during the excavations by Paul III. in 1546, and transported to the Vatican and the museum at Naples.
Note - this article incorporates content from Encyclopaedia Britannica, Eleventh Edition, (1910-1911)