Attributed traditionally to the king of Rome, Tarquin the Proud, this is the great sewer of Rome. It was the first of its kind, built to drain the then swampy area of the forum and make it habitable, and was a wonderous sight even in the later days of declining Rome. Originally, several streams met not far from the east end of the forum and flowed down the valley to empty into the Tiber. This resulted in very marshy conditions in the low areas until the construction of the Cloaca that took the stream underground and through an arch into the river that can still be seen beneath the modern Ponte Palatino, on the far side from the Ponte Rotto. Other fragments of the Cloaca can be seen, including a stretch beside a house near the Arch of Janus. At best traces exist of the original drain, and most of the work now visible dates to the reconstruction of the Cloaca by Agrippa.

The Tiber Island took its current shape in 292 BC when statue of Asklepios (or the Roman Aescapulas) was being brought to Rome and according to legend, the serpent sculpture on the staff came free and swam ashore here. Consequently a temple was constructed here and, though temples to other Gods later sprang up, the island was always linked with Aescapulas. The island was converted with heavy stonework to resemble a ship, with a prow and stern and even the sides, perhaps in the mid 1st century BC. The cult of Aescapulas was ever after associated with the island, and it became acknowledged as a place of healing. Interestingly a church-run hospital exists on the island even now.

The Pons Fabricius was constructed in 62 BC by Lucius Fabricius as recorded by inscriptions on the bridge itself. Restorations were carried out in 21 BC and these are also recorded thereon. The best preserved of Rome's ancient bridges, much of the bridge is original and the ends of the parapets are decorated with herms. It connects the Isola Tiburina with the city.

The true name of this, the oldest surviving bridge in Rome is the Pons Aemilius. It was the first stone bridge across the river, begun in 179 BC. Restored by Augustus, the bridge survived throughout the Empire, being badly damaged during floods in 1557. Again it was repaired, but in 1598 half the bridge was swept away and it was never to be truly repaired. In 1887 most of the rest of the bridge was destroyed in blasting to build the new banks of the river and now only one arch remains in the river, visible clearly from the banks and from the modern Ponte Palatine which runs next to it.