With respect to the present state of the old aqueducts, I can give you very little satisfaction. I only saw the ruins of that which conveyed the aqua Claudia, near the Porta Maggiore, and the Piazza of the Lateran. You know there were fourteen of those antient aqueducts, some of which brought water to Rome from the distance of forty miles. The channels of them were large enough to admit a man armed on horseback; and therefore when Rome was besieged by the Goths, who had cut off the water, Belisarius fortified them with works to prevent the enemy from entering the city by those conveyances. After that period, I suppose the antient aqueducts continued dry, and were suffered to run to ruins. Without all doubt, the Romans were greatly obliged to those benefactors, who raised such stupendous works for the benefit, as well as the embellishment of their city: but it might have been supplied with the same water through pipes at one hundredth part of the expence; and in that case the enemy would not have found it such an easy matter to cut it off. Those popes who have provided the modern city so plentifully with excellent water, are much to be commended for the care and expence, they have bestowed in restoring the streams called acqua Virgine, acqua Felice, and acqua Paolina, which afford such abundance of water as would plentifully supply a much larger city than modern Rome.
It is no wonder that M. Agrippa, the son-in-law, friend, and favourite of Augustus, should at the same time have been the idol of the people, considering how surprisingly he exerted himself for the emolument, convenience, and pleasure of his fellow-citizens. It was he who first conducted this acqua Virgine to Rome: he formed seven hundred reservoirs in the city; erected one hundred and five fountains; one hundred and thirty castella, or conduits, which works he adorned with three hundred statues, and four hundred pillars of marble, in the space of one year. He also brought into Rome, the aqua Julia, and restored the aqueduct of the aqua Marzia, which had fallen to decay. I have already observed the great number of baths which he opened for the people, and the magnificent thermae, with spacious gardens, which he bequeathed to them as a legacy. But these benefactions, great and munificent as they seem to be, were not the most important services he performed for the city of Rome. The common-sewers were first made by order of Tarquinius Priscus, not so much with a view to cleanliness, as by way of subterranean drains to the Velabrum, and in order to carry off the stagnant water, which remained in the lower parts, after heavy rains. The different branches of these channels united at the Forum, from whence by the cloaca Maxima, their contents were conveyed into the Tyber. This great cloaca was the work of Tarquinius Superbus. Other sewers were added by Marcus Cato, and Valerius Flaccus, the censors. All these drains having been choaked up and ruinous, were cleared and restored by Marcus Agrippa, who likewise undermined the whole city with canals of the same kind, for carrying of the filth; he strengthened and enlarged the cloaca maxima, so as to make it capable of receiving a large cart loaded with hay; and directed seven streams of water into these subterranean passages, in order to keep them always clean and open. If, notwithstanding all these conveniences, Vespasian was put to great expence in removing the ordure from the public streets, we have certainly a right to conclude that the antient Romans were not more cleanly than the modern Italians.