Palais des Thermes
Once the abode of the Roman government of Gaul, as well as of the kings of the first and second dynasties. Here Julius fixed his residence when he was Caesar of Gaul. It is in Paris, but the only part now extant is a vast hall, formerly the chamber of cold baths (frigidarium), restored by Napoleon III.
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894