Located at the very heart of Paris and visible from the main streets adjoining the museum, the Gallo-Roman Thermes de Cluny (baths) are among the largest ancient remains in northern Europe, notably thanks to the preservation of a vast vaulted room, the frigidarium.
In Roman times, the Northern thermae of Lutetia covered the area roughly mapped out by the boulevards of Saint-Michel and Saint-Germain, the Rue de Cluny and the Rue des Écoles. Covering an area of approximately 6,000 m², they constitute the largest public baths in this Gallo-Roman town whose administrative, religious and civil buildings descend in tiers from the Montagne Sainte-Geneviève to the Seine. Three operating levels have been unearthed, though only partially: a deeply buried hydraulic network (comprising sewer pipes and hypocaust pillars), underground utility rooms, and finally a ground floor comprising the frigidarium (cold room), caldaria (hot rooms) and palestra. The chronology of the buildings that make up the baths remains uncertain, but it is likely that they were built at the turn of the 1st or 2nd centuries AD and that they were in operation for no longer than two centuries.
The walls that have been conserved are distinctive for their high quality, made up of alternating layers of limestone rubble stone and horizontal bricks, in accordance with the opus vittatum mixtum technique. In the frigidarium, the most spectacular space still visible today, the visitor is invited to discover these facings as well as the original floor and the groin vault, which culminates at a height of almost 14 metres and still partly features its original coatings. Most of the decor is lost today, with the exception of the consoles of the frigidarium which are adorned with reliefs depicting ships. The mosaic representing Cupid riding a dolphin discovered close to the Hôtel de Cluny is perhaps another decorative element belonging to this room. These are signs that the decor may have had an aquatic theme which was popular in the Roman world, like in Pompeii, for example.
The Northern thermae of Lutetia were never completely ruined. Despite the troubles at the end of the Antiquity, a time when the elements were likely to have caused the most damage to the decor, the architectural spaces were conserved as they were occupied as of the early Middle Ages. Following that, the integration of the remains into the museum from the time of its creation and their listing as a Historic Monument in 1862 meant the monument was from then on protected as part of the nation’s heritage. In 2009, another important moment in its conservation was the restoration of the foundations and facings of the interior of the frigidarium, which gave the walls back their original rose colour, in true harmony with the intimate and grandiose space that was the Roman public bath.