VILLA ADRIANA. THE SMALL BATHS AND THE OCTAGONAL HALL
Villa Adriana had several thermal plants: the Small Baths, the Great Baths, the Baths with Heliocaminus and finally the small private baths of the Maritime Theatre.
They all had a path that gradually went from cold to heated rooms. The cold part, the frigidarium, had cold water pools. The heated part (tepidarium) was preceded by the changing room (apodyterium) and then had an heated area (caldarium) with hot water pools that ended in the so-called sudatio, a real burning sauna.
The heated rooms had a double floor, with a hollow cavity supported by brick columns (suspensurae): inside which hot air was circulated, coming from subterranean furnaces (praefurnia) in which wood was burned to heat the air and also the water for the pools.
To rationalize the management of the heating systems, all the thermal buildings of Villa Adriana were located in the same area, between the Poecile and the Vestibule, at a short distance from each other.
They were connected by a network of subterranean service corridors reserved for the slaves working the furnaces, which ended in the open with a carriage road that ran alongside the Hundred Chambers, and was used by the slaves who lived there and by the carts that transported the firewood and other supplies.
The Small Baths had cold, warm and heated rooms, pools for hot and cold water. The Frigidarium is perfectly preserved: it has two large pools for cold water once covered in white marble and accessible by steps.
Among the heated rooms of the Small Baths, the most important and spectacular is the Octagonal Hall, one of the masterpieces of the Villa's architecture. It was reopened to the public a few years ago after an endless restoration that consolidated its dome, providing it with a transparent covering.
The height of the dome is equal to its diameter, so here a perfect sphere can be inserted, as in the Pantheon in Rome.
The Hall has the shape of an octagon with concave and convex walls, which support a circular dome; the circle and the octagon were connected in an exceptional way, using only roman concrete (opus caementicium) with great mastery.
For this reason the Hall was designed, studied and admired by some of the greatest architects of the Renaissance and Baroque; and it still amazes modern architects today, given that it has no reinforced concrete.
From the doors of the Octagonal Hall amazing perspective views towards the surrounding areas, such as the large circular Sudatio PT18, can be seen.
The north-east side of the Small Baths is oblique and has reused a wall in opus reticulatum that belonged to the pre-existing villa of the Republican era that was later incorporated into Hadrian's Villa. In this way it was possible to connect the different orientation of the Building with Three Exedras and the Quadriporticus with that of the Vestibule (as seen in the plan).
The Small Baths were part of the Imperial Residence, the group of buildings reserved exclusively for the emperor, consisting of the Building with Three Exedras, the Garden Stadium, the Winter Palace, the Quadriporticus and the Small Baths.
The latter stood out from the other thermal buildings for the complexity of its architecture and for its precious marble decoration: some of the most beautiful opus sectile floors of the Villa have been preserved here.
This is why is disproved one of the most absurd "urban legends", according to which the Small Baths were reserved for women while the Great Baths were intended for men. Nothing can be further from the truth: users were differentiated by their rank, as shown by the pavements: precious marble ones for the Small Baths that were used only by the Emperor and his Court. Simple black and white mosaic floors in the Great Baths, which were reserved for the personnel, the officials and perhaps even the slaves.
Find out more about Villa Adriana in the book by Marina De Franceschini «Villa Adriana.. Architettura Celeste. I segreti dei Solstizi» (Italian edition only) and to this link