Aqua Claudia

Listen for a moment. Out here, the noise of Rome drops away. You may hear a dog barking across the grass, a train passing somewhere behind the trees, and the wind moving through the tall arches above you. The stone under your hand feels rough and slightly warm, pitted like old bread crust. Long lines of arches run across the open field, broken in places and whole in others. You are standing beside one of the greatest water machines of the ancient world.

This is the Aqua Claudia, one of the eleven aqueducts that fed ancient Rome. The emperor Caligula began it around the year 38. He did not live to see it finished. His successor, Claudius, completed it in the year 52, and the aqueduct carries his name. It opened together with a second channel, the Anio Novus, the New Anio. The two were built as partners, and for much of their route into the city they shared the same arches.

Here is the first surprise. Most of what you see is not the main part of the aqueduct. The Aqua Claudia ran for roughly sixty-nine kilometres, and most of that distance was underground. Its water came from springs in the hills near the upper valley of the River Aniene, east of Rome. The channel followed the land, cut into hillsides and buried in tunnels, dropping very slowly the whole way. Only near the city, where the ground fell away into this flat plain, did the engineers lift it into the air.

Why lift it at all? Roman aqueducts worked by gravity alone. There were no pumps. The water had to keep falling gently, metre by metre, from the springs to the city. Rome's hills meant the water needed to arrive high, so it could flow on to the higher districts. Across this low ground, the only way to keep that height was to build a line of arches tall enough to carry the channel. The arches are a bridge for a river that runs on top.

Look closely at the stone. The Romans built these arches from large, squared blocks of volcanic stone, laid without much mortar. The blocks are heavy and pale brown, with small dark specks. In many places you will also see bands and patches of red brick. These are not part of the first design. They are repairs, added over the following centuries as the aqueduct cracked and leaked. The structure carries the marks of generations of workers, all trying to keep the water moving.

The Roman writer Frontinus knew this aqueduct well. He was appointed water commissioner of Rome at the end of the first century, and he wrote a detailed book about the city's water supply. He counted the aqueducts, measured their flow, and complained about leaks and illegal taps. He praised the waters of the Claudia for their quality. His book still survives, and it is one of the main reasons we understand how this system worked.

Here is the second surprise. The channel is not one pipe. On top of the arches, the Aqua Claudia ran in a covered stone duct. Above it, the Anio Novus ran in a second duct. Two separate rivers travelled one on top of the other, each with its own water and its own source. If you look up at a broken section, you can sometimes see the hollow shape of these channels in cross-section, lined with a pinkish waterproof plaster.

The arches you see here grow taller as they approach the city. In places they rise more than twenty-five metres, roughly the height of an eight-storey building. Under the open sky of this park, they look almost light. But each pier is massive. Notice how wide the base is, and how the arches step in rhythm, one after another, until they shrink into the distance. That repetition is what makes the line so powerful to look at.

The aqueduct did not end out here. Its arches marched all the way to the walls of Rome. At the place now called Porta Maggiore, the two channels crossed two ancient roads on a grand double arch. Later, that arch was built into the city walls and became a gate. On its top you can still read long Latin inscriptions. One names Claudius as the builder. Others record repairs by the later emperors Vespasian and Titus, only a few decades after it opened.

Those repairs tell a story. The aqueduct had problems almost from the start. Stretches failed and had to be rebuilt. Later emperors added a branch, often called the Neronian Arches after the emperor Nero, to carry water toward the Palatine Hill, where the imperial palaces stood. Water was power in Rome. It filled baths, fountains and private houses, and an emperor who kept it flowing kept the city on his side.

After the fall of the Western Roman Empire, the system broke down. During the sieges of the sixth century, attackers cut the aqueducts, and much of Rome lost its running water. The city shrank toward the river. For centuries, these arches stood dry in open fields used for grazing sheep. Then, in the late sixteenth century, Pope Sixtus the Fifth built a new aqueduct, the Aqua Felice. In parts of this landscape it runs close by, and it reused older Roman structures along its way.

This field also has a life in cinema. The famous opening of Federico Fellini's film La Dolce Vita shows a helicopter carrying a statue of Christ over Rome. In those first moments, it flies past these same arches. Other Italian directors filmed in this area too. Today the park is a place for local life rather than tour groups. People jog along the paths, children play football in the grass, and families spread blankets in the shade of the stone.

Before you leave, look along the line one more time. Follow it with your eye toward the city, where the arches disappear among the buildings. Water once ran over your head here, silent and steady, day and night, for hundreds of years. Now there is only sky inside the channel. As you walk away, listen again for the wind in the arches... and notice how the light changes on the stone as the day moves on.