A drain before it was a sewer
The low ground between the Palatine and the Capitoline hills, where the Roman Forum would stand, was wet. Water ran down from the hills and had nowhere to go. The Forum began to take shape only at the end of the seventh century BCE, after the valley was drained. Roman tradition gave the credit to the kings: according to Livy, Tarquinius Priscus drained the low parts of the city around the Forum and the valleys between the hills, where water could not escape, with conduits that emptied into the Tiber. Livy adds that a later king, Tarquinius Superbus, set the common people to work on the Cloaca Maxima, the “greatest drain“, built underground.
So the first job of the Cloaca was drainage. Removing waste came later, as more water poured into it from the city above.
From ditch to tunnel
The Cloaca followed the line of an old watercourse. It ran from the Roman Forum along the Vicus Tuscus, wound through the Velabrum and the Forum Boarium, the low areas between the Palatine and the river, and after a wide curve reached the Tiber beside the Pons Aemilius, the bridge known today as Ponte Rotto. What began as an open channel was gradually lined with stone and covered with vaults, so that the city could build on top. Its mouth on the river is a triple arch of tufa blocks.
How big was it? By the time of Augustus, the geographer Strabo was impressed: Rome’s sewers, “vaulted with close-fitting stones”, had in some places room enough for wagons loaded with hay to pass through them.
Who kept it flowing?
Water did. A sewer works only if enough water runs through it to carry everything away, and Rome had plenty: Strabo says that the aqueducts brought water in such quantities that “veritable rivers” flowed through the city and its sewers. What flowed into the drains went on into the Tiber. In other words, the sewer was the second half of the water supply, and Strabo lists roads, aqueducts and sewers together as the works the Romans planned best.
Still working
The Cloaca Maxima is the largest Roman collector still in use. The main channel is preserved and can be walked for about 800 metres beneath the archaeological area in the centre of Rome, under the Forum of Nerva, the Roman Forum and the Velabrum; the last stretch and its monumental outlet, by contrast, are in poor condition. Drains were part of the plan of every Roman town that had water to dispose of, and Rome’s is the one that still works.
Where to see it
The interior is not open to the public: access is only through shafts, and Rome’s tourist board lists the monument as closed for safety reasons. You can see the outlet from the left bank of the Tiber near Ponte Rotto, and walk the route above ground from the Roman Forum through the Velabrum to the river.
Sources
- Livy, History of Rome 1.38.6 and 1.56.2 (Perseus).
- Strabo, Geography 5.3.8 (trans. Jones, LacusCurtius).
- Turismo Roma (Roma Capitale), “Cloaca Maxima”.
- FAI Fondo Ambiente Italiano, “Cloaca Massima” (I Luoghi del Cuore).
- Parco archeologico del Colosseo, “Foro Romano” (drainage of the valley, end of the seventh century BCE).
