Rome

magnificent sight of the tall aqueducts converging on Rome, across the flat wastes of the Campagna—mile upon mile of arches not yet fallen into ruin, imposing their proud rhythm on an otherwise undistinguished landscape, silently beautiful in the golden morning or rosy evening light.

But how to give them the necessary shape, the exact fall needed to convey the precious water into the heart of the city? This was accomplished by surveyors. They did not have modern equipment—the laser levels and theodolites of today’s surveyors did not exist. Yet they managed well with what would seem, by modern standards, to be very primitive instruments. The first of these was the chorobates, or water level, a long narrow trough (a straight, hollowed-out section of tree trunk would do) which could be propped up on stones and filled with water. Since a still water surface is always horizontal, this gave an excellent reference for sighting along, and when an assistant placed himself some distance away with a vertical, graduated measuring rod which had a movable target, a surveyor with good eyes—Rome had no lenses or optical glass—could readily establish the rise or fall of the land between the two points. It was a clumsy instrument, needing a twenty-foot-long table to carry the trough, but in skilled hands it could plot variations in height with astonishing accuracy. Though no ancient remains of such a device have ever been found, descriptions leave no doubt about its use. Similar surveying principles governed the boring of underground tunnels.

Next in usefulness was the dioptra, a flat disc mounted on a tripod, which could be both turned horizontally and tilted in the vertical plane. Through a sighting tube fixed diametrically across the disc, it could measure both the height and the bearing of a distant target and was thus the ancestor of the modern theodolite.

Finally, there was the basic tool that every surveyor had to have, more for field surveying than for the layout of aqueducts: the groma, consisting of two horizontal crosspieces fixed at right angles on the tip of a pole, with a plumb bob hanging from each end of the pieces. It was indispensable for the other kind of big Roman engineering project as well: the laying out of roads.

Along the length of the aqueduct, and especially just before it entered Rome, settling tanks were built: a simple filtration system whereby the flow was allowed to pause so that particles and debris could sink to the bottom, there to be cleaned out periodically by the slave maintenance crews.

The oldest of the aqueducts dated well back into republican days: the Aqua Appia, sixteen kilometers long, mostly underground, built in 312 B.C.E. and successively restored by Quintus Marcius Rex (144 B.C.E.), Agrippa (33 B.C.E.), and Augustus (11–4 B.C.E.). It delivered seventy-five thousand cubic meters of water per day.

The next oldest was the Anio Vetus (272–69 B.C.E.), another mostly subterranean aqueduct, which took its water directly from the Tiber above Tivoli, bringing it eighty-one kilometers to Rome and supplying some 180,000 cubic meters a day.

Rome’s need for water increased rapidly in the second century B.C.E., as a result of its colonial victories, which increased the population of the city. This produced the longest of all its aqueducts, the Aqua Marcia, which ran for 91 kilometers (81 kilometers below ground) and delivered 190,000 cubic meters daily.

Agrippa, builder of the Pantheon, also constructed two aqueducts, the Aqua Julia (33 B.C.E.) and the Aqua Virgo (so called because its source outside the city was pointed out to his surveyors by a young girl). Between them they brought some 150,000 cubic meters a day into Rome. Two aqueducts started by the Emperor Caligula (the Aqua Claudia in 38 C.E., the Aqua Anio Novus in the same year) had to be finished by the Emperor Claudius; between them, they gave Rome a further 380,000 cubic meters a day. All in all, the eleven aqueducts provided some 1.13 million cubic meters of water to meet the daily requirements of about a million people, which averaged out at about 1.13 cubic meters of water per person per day.

Not all this water was used for drinking, cooking, and washing. Water also had a strong—indeed, essential— decorative and metaphorical aspect in ancient Rome, as it does today. Not every house had a garden, but many did, and those fortunate enough to have one needed a good supply of water for plants, pools, and, of course, fountains. The fountains of Rome, celebrated in numberless paintings and poems as well as in music—one thinks of the charming trills and tinklings of Respighi’s Le fontane di Roma—have always been a feature of the city and the culture it embodied. Because of the low water-pressure in the days before mechanical pumps, the “abounding glittering jet” that spells “fountain” to us today and was so magnificently choreographed by the likes of Gian Lorenzo Bernini in the seventeenth century was not available in ancient Rome, but a lot of refreshment and relaxation could be had from trickling basins, ornamental pools, shallow waterfalls, and chasses d’eau—the most grandiose project of this kind being the celebrated Canopus in the garden of Hadrian’s Villa at Tivoli.

All this civic splendor, and much more, depended on a colonial empire which had grown from a small seed in Italy, at the mouth of the Tiber—Ostia, that vital port where the wealth of the growing empire came in and the administrative manpower went out, taken from its original inhabitants in Etruscan times. Now, at the turn of the millennium, its spread was prodigious. In Africa, Rome commanded the provinces of Numidia, Mauretania, Cyrenaica, and Africa Proconsularis. Its African possessions did not supply mineral wealth (that came largely from Spain), but they gave Rome huge supplies of grain and other foodstuffs and, as a bonus, supplied the wild animals for the shows in the arenas. Rome had all of Egypt. Its command of the Iberian Peninsula, modern Spain and Portugal, was divided between the provinces of Tarraconensis, Lusitania, and Baetica. It ruled Gaul (Lugdunensis, Narbonensis, Belgica) and Britain. It had—insecurely, at times—the frontier provinces of Germany and the lands along the natural frontier of the Danube, such as Dacia. It had annexed Greece (Macedonia, Achaea, and Thrace) and much of Asia Minor. Its farthest Eastern Provinces included Judaea, Syria, and Mesopotamia.

At its height, the Roman Empire included fifty to sixty million people—all under the absolute rule of one single man, all members of subject populations: citizens of Rome, but also other Italians; Europeans and Middle Easterners of all sorts, Gauls, Dacians, Armenians, Mesopotamians, Syrians, Africans, Egyptians; Britons, Spaniards, Germans, and so on, seemingly ad infinitum. These formed a vast and bewilderingly complex mosaic of languages, histories, creeds, and customs, some willingly passive to Roman authority, most of them manageable by dint of colonial firmness, and a few—such as the ever-fractious Jews— continually at odds with the system that had taken them over. Some of these peoples had very little effect on the core culture of Rome. Others, notably Greece, not only influenced but transformed it. “Graecia capta ferum victorem cepit,” wrote Horace, “et artes intulit agresti Latio”: “When Greece was taken she enslaved her rough conqueror, and introduced the arts to cloddish Latium.”

Almost as soon as he had emerged victoriously from the Battle of Actium in 31 B.C.E., Augustus launched into an ambitious program to restore his city’s damaged prosperity. He took advantage of the long-term security of funds and work which his principate—the word given to his rule as Princeps or “First citizen,” a title Augustus had chosen to avoid the taint of absolutism or kingship—allowed. “Professing himself satisfied with the tribunician power for the protection of the plebs,” wrote Tacitus,

Augustus enticed the soldiers with gifts, the people with grain, and all men with the allurements of peace, and gradually grew in power, concentrating in his own hands the functions of the Senate, the magistrates, and the laws. No one opposed him, for the most courageous had fallen in battle.… As for the remaining nobles, the readier they were for slavery, the higher they were raised in wealth and offices.

It was an essential part of Augustus’ political genius that, now and over the coming decades of his reign, he successfully maintained the illusion that he was not a dictator, just a savior, the man who had restored the Republic