The Servian City. Tradition ascribes to Servius Tullius the building of the famous wall which surrounded Rome during the historical period, the remains of which are still to be seen. These remains, however, are in large part not earlier than the fourth century B.C., belonging to the period after the invasion of the Gauls. It is probable, therefore, that this wall of the fourth century was a complete rebuilding of much weaker fortifications that had existed for a long time, and that it followed in the main the earlier line, but with some variations. The evidence of literature and inscriptions and the remains of the wall itself enable us to trace this line in its final course with certainty at almost every point. It coincided with the probable wall of the city of the Four Regions from the southwest corner of the Capitoline along the edge of the Quirinal, but extended almost a kilometre farther northeast, to a point near the junction of the tableland behind the Quirinal and the collis hortorum, the present Pincian hill. Thence it ran southeast and south until it again approached the line of the city of the Four Eegions on the Oppius. Following closely, or coinciding with, this line round the Caelian, it diverged at the porta Capena, and inclosed the Aventine, passing along its slope to the northern corner, where it bent at right angles and continued in a straight line to the Tiber, here only about 125 metres distant from the hill. From the southwestern corner of the Capitoline, it was also built in a direct line to the river. This left a distance of about 300 metres along the river bank where there was no wall like that which surrounded the rest of the city. Recent excavations have brought to light the remains of stone quays built along the bank, and doubtless provided with a sort of parapet, which would prevent an enemy from making a landing.
The area added to the city was in two sections, that on the northeast tableland, stretching back from the Quirinal and Esquiline to the new wall, and that on the south, the whole region of the Aventine and the low ground between the Palatine, the Forum, and the Capitoline. A large part of this newly acquired district was covered with woods, and continued to be so until the later days of the republic, as is shown by Varro's descrip- tion of the situation of the sacraria Argeorum, which in certain parts of the city, as on the Aventine and the Esquiline, are described as being near this or that grove.
For much the greater part of its course this wall was built along the edge of the cliffs in the manner of the Palatine fortifications, an independent wall being necessary only where low ground or the end of a valley had to be crossed, as between the hills and the river or between the Caelian and the Aventine, except for the long stretch across the plateau of the Quirinal and the Esquiline. Here, instead of an ordinary wall, the famous agger was erected.
Dionysius states that the length of the Servian wall was the same as that of the wall of Athens, 43 stadia, or 5 3/8 Roman miles, and this corresponds very closely with the line as it can now be traced. Communication with the opposite bank of the Tiber was secured by the pons Sublicius. This wooden bridge was the only one in existence until 179 B.C., and is usually supposed to have spanned the river close by the forum Boarium, within the limits of the Servian fortifications.
The Servian city marked a most important departure from the earlier conception of the city, or urbs, in that the line of the pomerium, and therefore the city-templum, was not extended to coincide with the new wall, but remained as it had been during the previous period. The new Esquiline and Aventine regions remained without the sacred precinct. The reason for this condition is unknown, but from the time of Sulla the political fiction was developed that no one who had not increased the area of Roman territory by actual conquest had the right to extend the pomerium of the city.
Latin literature speaks of many gates in the Servian wall, and gives the names of sixteen which are accepted as authentic. Of these, the site of some can be made out with certainty, of the others with more or less probability.
Vincenzo Fasolo, "The Campo Marzio of G. B. Piranesi".
Pagan - Christian - Triumphal Way