Pons Cestius

Listen first to the water. Below you, the Tiber splits around a small island and runs fast and brown through a narrow channel. The sound is steady, a low rushing that never quite stops. Under your feet, the stone is pale and worn smooth. You are standing on one of the oldest river crossings in Rome. It is a bridge that Romans have walked across, in one form or another, for more than two thousand years.

This is the Pons Cestius. Romans today call it Ponte Cestio. It links Tiber Island to Trastevere, the old neighbourhood on the river's western bank. On the other side of the island, a second ancient bridge, the Pons Fabricius, reaches the eastern bank. Together the two bridges turn this small island into a stepping stone. For centuries, it was one of the easiest ways to cross the river in the heart of the city.

The first stone bridge here dates to the first century before Christ, near the end of the Roman Republic. It takes its name from a man called Cestius. Historians are not certain which Cestius he was. Several men of that family name held public office in this period, and the records do not settle the question. So the bridge carries a name, but the person behind the name remains a small mystery.

The bridge you see today is not simply that first one. In the fourth century after Christ, the bridge was rebuilt under the emperors Valentinian, Valens and Gratian. It was even given a new official name — the Bridge of Gratian. Look along the stone parapet. Latin inscriptions from that rebuilding still survive there. They record the emperors' work in formal, carved capital letters. Very few visitors stop to read them. Most walk straight past.

Here is the first surprise. Some scholars believe the fourth-century builders reused travertine from older monuments nearby. The Theatre of Marcellus, just across the river, is often mentioned as a possible source. Travertine is the creamy, slightly pitted limestone that much of ancient Rome was built from. If this is true, the stones under your feet may have stood in another building before they became a bridge. Romans recycled their city constantly, and this bridge may be one more example.

In the Middle Ages, the bridge took yet another name. People called it the Bridge of Saint Bartholomew, after the church on the island. Rome had shrunk dramatically by then. Much of the ancient city was fields and ruins. But Tiber Island stayed busy. Pilgrims, traders and the sick still crossed here. A bridge that the emperors had dedicated now served a city of churches, monasteries and small river trades.

Now the second surprise. The bridge you are standing on was taken apart in the late nineteenth century. After Rome became the capital of a united Italy, engineers built tall stone embankments along the Tiber to stop the floods that had damaged the city for centuries. The river channel here was widened. The old bridge no longer fit. So the builders dismantled it and rebuilt it, reusing original stones in the central arch where they could.

That is why the bridge looks the way it does. The original design had one large central arch with smaller openings on either side. The rebuilt bridge has three arches, and the central one follows the ancient arch most closely. Look down at the river and compare the arches. The middle one is the heart of the old structure. The side arches belong to the modern rebuilding. So this is an ancient bridge, but also a careful nineteenth-century reconstruction.

Turn toward the island itself. Tiber Island is shaped a little like a boat, long and pointed at each end. Legend has it that the island formed from grain thrown into the river after the last king of Rome was driven out. It is a story, not history, but Romans told it for centuries. Better documented is the temple to Aesculapius, the Greek god of healing, built on the island in the early third century before Christ.

That link to healing never really ended. A hospital still stands on the island today. The Basilica of Saint Bartholomew rises on the site associated with the old temple. For more than two thousand years, people have crossed these bridges looking for a cure. When you watch someone in a hospital uniform walk across, you are seeing a very old pattern continue in a modern form.

Now look downstream, to the south. In the river stands a single broken arch, alone in the water and attached to nothing. Romans call it Ponte Rotto, the Broken Bridge. It is what remains of the ancient Pons Aemilius, a bridge that floods damaged again and again until it was finally left as a ruin. Seeing it from here shows you why a bridge like the Pons Cestius survived only through constant repair.

This spot is also a good place to understand the river's two levels. High above, the city traffic runs along the embankment roads. Below, a paved walkway follows the water's edge. In warmer months, the island and the riverbanks fill with people. There are cafés, summer events, and couples sitting along the stone steps. In winter, the river can rise high and fast, and the lower path sometimes floods.

Before you move on, rest your hand on the parapet for a moment. Feel the cool, slightly rough stone. Some of it was cut in the fourth century, and some was set in place in the nineteenth. Ahead of you lie the narrow streets of Trastevere. Behind you, the island and the hospital. And under you, the Tiber keeps running, just as it did when the first Roman builders measured this short crossing.