The ruin with which it was identified, formerly called turris Mæcenatis, or Frontispicium Neronis, has now been pulled down, but a part of it, and especially one huge mass of carved marble, remains in the Colonna Gardens. Representations of the Frontispicium Neronis as it was before its destruction, may be seen in Donatus and the older topographers. The fragments of stonework are now thought to have belonged to the entrance of the Thermæ of Constantine.
The site of the building erected upon the Quirinal by the mad emperor Heliogabalus, and called Senaculum Mulierum in which he assembled the Roman matrons for consultation about the laws of fashion in dress and manners, is not known.
The site of the Thermæ of Constantine, which are placed by the Notitia next to the Capitolium antiquum, is tolerably well defined by the notices of the Anonymous MS. of Einsiedlen, and by an inscription found near the Quirinal Palace, recording their restoration by Petronius Perpenna probably in the year 443. Both of these indicate the Palazzo Rospigliosi as standing upon the ground once occupied by the central building of the Thermæ. The Anonymous MS. mentions the Thermæ on the road between the Church of S. Agata and that of S. Vitale. Pozzio, Albertini, Fulvius, Q. Fauno, and Gamucci, all agree in confirming this evidence. Large portions of the ruins were still standing in their time, and in Du Perac’s views, published in the seventeenth century, the central part of the buildings is represented. Another part of the ruins of these baths was found in the construction of the Quirinal Palace in the time of Paul V.
Statues found in the Thermæ of Constantine.
There can be no doubt that these Thermæ, which were of great extent, reached nearly across the Quirinal Hill, occupying the sites of the present Palazzo Rospigliosi, part of the Colonna Gardens and the Quirinal Palace. Three statues were found in the ruins, representing Constantine and two of his sons. These are supposed to have stood near the grand entrance of the Thermæ. The first is now in the Portico of the Lateran Basilica, the two others were placed by Paul III. on the balustrade of the Piazza Capitolina. The famous pair of the Dioscuri and their horses, which now ornament the Piazza di Monte Cavallo, were also discovered on this site. The history of these well-known sculptures cannot be traced farther back than the time of Constantine, whose Thermæ they adorned. The old tradition which states that they were a present from Tiridates to Nero is in some degree supported by the mention of the equi Tiridatis in the Notitia, but is not confirmed by any other evidence. That they are not rightly supposed to represent the Dioscuri can hardly be doubted, and the inscriptions which ascribe them to the chisels of Phidias and Praxiteles respectively are erroneous. For not to mention that the exact reproduction of nature in its highest type of symmetry, peculiar to the style of the highest Greek art is absent, and that we find instead the conventional mode of representation characteristic of the revival of art under the emperors, it seems hardly possible that Praxiteles, who lived more than half a century after Phidias, should have occupied himself in imitating and completing a group begun by his predecessor.
These colossal figures and the statues of Constantine mentioned above, probably stood in the grand court of the Thermæ. There are now no traces left of the outer enclosure of this court, but the plan of the central blocks of buildings has been preserved by Palladio, in whose time there was doubtless a sufficient portion left to enable him to reconstruct the whole. It is somewhat different from the plan of most of the other Thermæ, having a large semicircular court on one side surrounded with arcades, the purpose of which has not been discovered. The other halls and apartments are of the usual size and shape, with the exception of the exedræ, which are rectangular. At one side of the enclosing court, apparently the north side, there was a large theatre similar to that at the baths of Titus.
Some of the older topographers had conjectured that the ruins in the Colonna Gardens, wrongly, as has been shown, ascribed to Aurelian’s Temple of the Sun, and also the massive substructions and stairs which have been found behind the stables of the Quirinal Palace on the west slope of the hill, belonged to the Thermæ of Constantine. This conjecture has been revived and ingeniously supported by Professor Reber, who remarks that the outer court of the Thermæ, to judge by the extent of that of the baths of Diocletian or of Caracalla, may very well have reached across the whole breadth of the hill from east to west, and further that the approach to the Thermæ would naturally be placed on the west side, where the Imperial fora lay. If so, the building called the tower of Mæcenas stood exactly in the position at the summit of the colossal flight of stairs now hidden under the Papal stables which would answer to the entrance portico of the Thermæ. The fragments of the so-called Tower of Mæcenas are very similar to those of the portico of Octavia, which was also the entrance to a grand enclosure. They consist of two huge blocks of marble, the largest of which is seventeen feet in length, ornamented with mouldings of the usual Corinthian character, and with a frieze beautifully decorated with festoons of foliage enclosing birds and genii. The style is of a late epoch, and might very probably belong to the Constantinian age.