The capital of Latium required another and more complete system of defence; they proceeded to construct the Servian wall. The new continuous city-wall began at the river below the Aventine, and included that hill, on which there have been brought to light recently (1855) at two different places, the one on the western slope towards the river, the other on the opposite eastern slope, colossal remains of those primitive fortifications--portions of wall as high as the walls of Alatri and Ferentino, built of large square hewn blocks of tufo in courses of unequal height--emerging as it were from the tomb to testify to the might of an epoch, whose buildings subsist imperishably in these walls of rock, and whose intellectual achievements will continue to exercise an influence more lasting even than these. 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. With this is connected the fact, that for purposes strictly urban, such as the distribution of the introduced water, the inhabitants of Rome were divided into the inhabitants of the city proper (-montani-), and those of the districts situated within the general ring-wall, but yet not reckoned as strictly belonging to the city (-pagani Aventinensis-, -Ianiculenses-, -collegia Capitolinorum et Mercurialium-).(13) The space enclosed by the new city wall thus embraced, in addition to the former Palatine and Quirinal cities, the two federal strongholds of the Capitol and the Aventine, and also the Janiculum;(14) the Palatine, as the oldest and proper city, was enclosed by the other heights along which the wall was carried, as if encircled with a wreath, and the two castles occupied the middle.
The work, however, was not complete so long as the ground, protected by so laborious exertions from outward foes, was not also reclaimed from the dominion of the water, which permanently occupied the valley between the Palatine and the Capitol, so that there was perhaps even a ferry there, and which converted the valleys between the Capitol and the Velia and between the Palatine and the Aventine into marshes. The subterranean drains still existing at the present day, composed of magnificent square blocks, which excited the astonishment of posterity as a marvellous work of regal Rome, must rather be reckoned to belong to the following epoch, for travertine is the material employed and we have many accounts of new structures of the kind in the times of the republic; but the scheme itself belongs beyond doubt to the regal period, although presumably to a later epoch than the designing of the Servian wall and the Capitoline stronghold. The spots thus drained or dried supplied large open spaces such as were needed by the new enlarged city. The assembling-place of the community, which had hitherto been the Area Capitolina at the stronghold itself, was now transferred to the flat space, where the ground fell from the stronghold towards the city (-comitium-), and which stretched thence between the Palatine and the Carinae, in the direction of the Velia. At that side of the -comitium- which adjoined the stronghold, and upon the stronghold-wall which arose above the -comitium- in the fashion of a balcony, the members of the senate and the guests of the city had the place of honour assigned to them on occasion of festivals and assemblies of the people; and at the place of assembly itself was erected the senate-house, which afterwards bore the name of the Curia Hostilia. The platform for the judgment-seat (-tribunal-), and the stage whence the burgesses were addressed (the later rostra), were likewise erected on the -comitium- itself. Its prolongation in the direction of the Velia became the new market (-forum Romanum-). At the end of the latter, beneath the Palatine, rose the community-house, which included the official dwelling of the king (-regia-) and the common hearth of the city, the rotunda forming the temple of Vesta; at no great distance, on the south side of the Forum, there was erected a second round building connected with the former, the store-room of the community or temple of the Penates, which still stands at the present day as the porch of the church Santi Cosma e Damiano.