Within this circumference, Rome was contained after the _agger_ of Servius Tullius was completed. This agger was an enormous work: it ran, almost an Italian mile, from the Colline to the Esquiline gate, and was a moat of one hundred feet in breadth and thirty in depth, the earth of which was thrown up as a mound lined with a wall and fortified with towers. In the time of Augustus this work was not only still discernible, but was used as a promenade, a kind of boulevard, of which Horace says, _aggere in aprico spatiari_; it continued to be admired even in Pliny’s time, while the other walls were already destroyed. At present only few traces of it are visible; but I have no doubt that by excavations the lining wall might still be discovered. In some parts, the agger is still discernible as a continuous hill. Through this agger, then, the whole city became one united place. Although the city became greatly extended, by incorporating with itself suburbs and other hills, yet the additional hills were not counted, and Rome remained the city of the seven hills. One of the additions which the city received, was that of the _mons Pincius_ or _Hortulorum_, on the other side of a wide valley, by which it was separated from the Quirinal: it derived its name from the palace of the Pincii, of which the ruins were to be seen as late as the sixteenth century; it is also remarkable as the place where Belisarius in the sixth century had his head-quarters. Near the Aventine, another hill was added, to which the ancients do not give a distinct name, but which, during the middle ages, was strangely called _Asbestus_, which is perhaps a corruption of an ancient name. If it be not a mere invention, it is probable that a church may have stood there which was called _in Asbesto_. Nibby was the first to notice this, at least he first published it.[7] The suburb beyond the bridge (_trans Tiberim_, _Trastevere_) also was added, and in like manner the _Janiculus_ became a part of the city, as well as another small hill in the neighbourhood of the second Aventine, the greater part of which, however, was outside the city. The number of hills which were regarded as belonging to the circumference of the city, thus already amounted to ten. In the ninth century, when the Borgo was built and St. Peter was fortified, the Vatican hill also was incorporated, so that at present the number of hills belonging to the city amounts to eleven. A great part of them, however, is now uninhabited, being covered by vineyards. But the division into seven parts had taken such firm root, that Augustus, in dividing the city into regions for the purpose of regulating the administration of the police, made fourteen regions; and this was wise and not a pedantic going back to obsolete institutions. This arrangement of Augustus was very necessary, for Rome was at that time little better than a den of robbers, as is usually the case in republics when the free constitution is not kept