The ring-wall further embraced the Caelian and the whole space of the Esquiline, Viminal, and Quirinal, where a structure likewise but recently brought to light on a great scale (1862)--on the outside composed of blocks of peperino and protected by a moat in front, on the inside forming a huge earthen rampart sloped towards the city and imposing even at the present day--supplied the want of natural means of defence.

From thence it ran to the Capitoline, the steep declivity of which towards the Campus Martius served as part of the city-wall, and it again abutted on the river above the island in the Tiber.

The Tiber island with the bridge of piles and the Janiculum did not belong strictly to the city, but the latter height was probably a fortified outwork.

Hitherto the Palatine had been the stronghold, but now this hill was left open to be built upon by the growing city; and on the other hand upon the Tarpeian Hill, standing free on every side, and from its moderate extent easily defensible, there was constructed the new "stronghold" (-arx-, -capitolium-( 10)), containing the stronghold-spring, the carefully enclosed "well-house" (-tullianum-), the treasury (-aerarium-), the prison, and the most ancient place of assemblage for the burgesses (-area Capitolina-), where still in after times the regular announcements of the changes of the moon continued to be made.

Private dwellings of a permanent kind, on the other hand, were not tolerated in earlier times on the stronghold-hill;( 11) and the space between the two summits of the hill, the sanctuary of the evil god (-Ve-diovis-), or as it was termed in the later Hellenizing epoch, the Asylum, was covered with wood and presumably intended for the reception of the husbandmen and their herds, when inundation or war drove them from the plain.
The Capitol was in reality as well as in name the Acropolis of Rome, an independent castle capable of being defended even after the city had fallen: its gate lay probably towards what was afterwards the Forum.( 12) The Aventine seems to have been fortified in a similar style, although less strongly, and to have been preserved free from permanent occupation.