THE THERMÆ of Septimius Severus and Commodus were close to each other, and probably connected. They are mentioned together in the Regionary Catalogue as in the first Regio, and there are remains of them under the small hill, called Monte d’Oro, probably, from the golden colour of the sand in its original state, which is situated just within the Porta Latina, between that and the Porta Metronia. Some excavations were made there in 1870 by the Archæological Society, and large subterranean chambers and corridors were found similar to those under the Thermæ of Antoninus Caracalla. The _specus_ of an aqueduct was also followed for a considerable distance in the direction of the Porta Latina. This must have been for the Aqua Severiana. Just outside of that gate are remains of two _piscinæ_ or _castella aquarum_, one on either side, and on different levels. One of these belonged to the Aqua Aurelia, the other to the Severiana. The course of this latter is more doubtful, but it was probably only a branch from one of the great aqueducts, and would appear to have come in the bank on which that part of the wall of Aurelian was built, from the Porta Metronia to the Porta Latina. It arrived at the bridge over the Almo (on which the gateway-arch of the Porta Metronia is built), from the great _piscina_ and _castellum aquæ_, on the cliff of the Cœlian, near the Porta Capena and the Camenæ, where two aqueducts are now visible, having been brought to light by the excavations of the Archæological Society. The construction of one of these aqueducts agrees with the time of Septimius Severus. XIV. ANTONINIANA, A.D. 215. This aqueduct enters Rome at the south-east corner near the Porta di S. Sebastiano, and passes over the arch of Drusus; a part of the arcade is visible by the side of it. The _specus_ can be seen both in the wall of the city, through which it passes, and over that arch, and one of the arches of the arcade remains on the east side of it. It was carried in that manner for some distance across the valley or foss, until it reached the high bank of earth on which the Wall of Aurelian is built, near the Porta di S. Sebastiano, and then along the edge of that bank, which is the great _agger_ of the ancient earthworks, against the outer side of which the Wall of Aurelian is built. The inner side of the bank is supported by a low wall here as in many other parts, and upon or against that inner wall the _specus_ of the aqueduct is carried. It is sometimes on an arcade, in other parts it is carried on the wall to the Thermæ of Antoninus Caracalla. The demolition of part of this arcade in modern times is recorded by contemporary authors.