CLOACAE

In the Colosseum, rainwater was collected on the cavea by concentric ducts and poured into vertical pipes leading to the ground floor. From there the water flowed partly towards the arena and partly towards the outside, because of a double incline of the floor. On the outside of the building, water (including that of the surrounding square) was drained into a brick conduit (60 cm wide and 160 cm deep) which surrounds the Colosseum 2 metres below ground just outside the first step at the base. At regular intervals along this drain there are wells that go 8 metres deep, down to a much bigger drain that also surrounds the amphitheatre. This drain was probably connected to the main sewer, which passes along Via di S. Gregorio, under the Circus Maximus and reaches the Tiber river near the Church of the "Bocca della verità".

One would think that these four collectors would carry the water to the big elliptical drain placed 8 metre deep around the monument, but recent studies have demonstrated that outgoing water was drained only by the southern main axis collector, since it appears that the other three drains are not connected to the internal elliptical collector (see the picture on top of the page).

It is not clear, therefore, if all four drains are connected to this external one. As far as we know, these drains were built at the same time of the foundations, by casting the cement over wooden boxing more than 50 metres long. The floor of these conduits – made in Domitian’s time – was paved with bricks and it was carefully sloped in order to have the right incline. The huge dimension of these conduits has led some (Mocchegiani) to think that they had been planned, from the beginning of the construction, to carry the enormous quantity of water necessary to fill up the arena for the naumachiae, and that later, in Domitian’s time, this project may have been abandoned. This could explain why ancient authors wrote about naumachiae held in the Colosseum. Naumachiae could have been organized maybe in Titus’ time; later, when the underground of the arena was set up, this became impossible

There are doubts, however, about the function of many conduits of the amphitheatre. Recent studies (Lombardi and Corazza) have found evidence of fountains in the Colosseum. Some (Luciani) suggest that the pipes and ducts spread here and there may be leader pipes, i.e. carried water inside, not outside. It is common sense to think that so many people, gathered under the sun for so many hours needed some refreshment, and indeed some have believed to have found traces of fountains on different floors.

Right: a map of the main sewers of ancient Rome: the Colosseum waters ended in the F drain.

The drains on the shorter axis were excavated between 1974 and 1980 by the then Director of the monument, Claudio Mocchegiani Carpano. The sediments were analysed by Professors Devoto and Parotto. In the silt they found remains dating back to the IV-V century, i.e. the time in which the conduits got clogged up. There were small bones of animals (chickens, sheep, pigs, goats), both exotic and domestic, probably destined to be eaten by the spectators or by the staff of the amphitheatre. It is therefore believed that bigger bones were recycled in order to craft objects. They also found many fruit pits and seeds, well preserved in the silt. We know from this finding that the Romans ate figs, olives, nuts, peaches and melons. Luciani (Il Colosseo) observes that it is all summer fruit, so it easy to think that the shows were all held during the good season. Pieces of pottery, mainly oil lamps, and even a tabella defixionum, a kind of thin plate used for sorcery, were also found inside the drains

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