Cloaca maxima


  • Cloaca maxima zu Beginn der Späten Republik (um 200 v.Chr.), Verlauf über Forumsfläche
  • Cloaca maxima zu Beginn der Späten Republik (um 200 v.Chr.), Verlauf über Forumsfläche
  • Cloaca maxima zu Beginn der Späten Republik (um 200 v.Chr.), Verlauf über Forumsfläche
  • Cloaca maxima (6. Jh. – frühes 2. Jh. v.Chr.)

Constructed: 6th century B.C.

Alterations: it was covered in the early 2nd century B.C.; further alterations were made in the subsequent period to stabilise and redirect it

Function: sewage and drainage system

Historical Context: Late Republic I

Even though the Cloaca Maxima is almost completely hidden from view today, it was a crucial element in helping the Forum develop into the central public space of ancient Rome. This drain made it possible to drain the lower area of the Forum, which was frequently flooded by the Tiber. Only this method could allow this area to serve as the building ground for ongoing settlement and construction. The Cloaca Maxima was installed by the last kings of Rome in the 6th century B.C. As an open ditch it divided the Forum along a north-south-axis. It was later covered, probably in the 2nd century B.C., and vanished from sight in the Forum. It continued to serve the Forum as an underground drainage channel.

History and Function

During the early period of Roman settlement, the area of the later Forum was constantly flooded by the Tiber River and by smaller streams flowing from the Quirinal Hill, Viminal Hill, Esquiline Hill and Palatine Hill down into the valley and then the Tiber, south of the Forum. Archaeological evidence shows clearly that during the early phases of the 7th and 6th century B.C. the ground level of the Forum had to be kept stable by tamping the ground – but this destroyed huts and buildings which then had to be repeatedly rebuilt. In order to counteract this continual threat and transform the Forum area into an urban space that could be reliably used, a big drainage system was built in the course of the 6th century B.C. It ran from the north to the south of the Forum and drained the valley. Some literary sources from a later time period ascribe this measure to either the fifth king, Tarquinius Priscus, or the last king, Tarquinius Superbus. Regardless of how one reads these sources, the fact that this was ascribed to one of the Roman kings reveals how strongly the Romans felt about the prestige of this ambitious construction project.

In the first centuries of its existence, the Cloaca Maxima cut across the Forum as an open channel and divided the Forum area, physically and visually, into two spaces. These corresponded to the two functional centres of the Forum area. The first space was located in the west, with the Comitium and the Curia, and acted as the place for the procedures of political decision making. The second space was located in the east, with the Regia and the Temple of Vesta, and constituted the central sacral area of the Forum.

Scholars disagree about when exactly the Romans covered up the open channel, thereby changing it into an underground drainage system. Whereas older research concluded that this must have taken place in the late 6th or 5th century B.C., newer studies have argued (plausibly) that this occurred much later. According to the latter studies, the Romans covered over the Cloaca Maxima in the early 2nd century B.C. and thereby caused it to disappear from the face of the Forum. From that time on it served as an underground drainage system, and over time it underwent numerous repairs and extensions.


Our reconstruction of the Cloaca Maxima only depicts the phase in which it was visible as an open ditch cutting across the Forum. It was massively constructed, using blocks of tuff around 3 m long and 3 m wide. It seems likely that there was a wooden balustrade along the sides of the channel through the Forum so that carts, horses and visitors (during crowded gatherings) would not fall into it. Incisions made into the tuff blocks indicate beams that allowed the visitors of the Forum to cross the channel.


A more detailed discussion and scholarly reconstruction can be found in the wiki of the digital Forum Romanum (Erika Holter, Julia Preis)


Selected Bibliography

H. Bauer, Cloaca maxima, in: E.M. Steinby (ed.), Lexicon Topographicum Urbis Romae I (Rome 1993) 288-290.

H. Bauer, Die Cloaca Maxima, Mitteilungen. Leichtweiss-Institut für Wasserbau der Technischen Universität Braunschweig 103, 1989, 43-54.

J. N. N. Hopkins, The Cloaca Maxima and the Monumental Manipulation of Water in Archaic Rome, The Waters of Rome 4, 2007, 1-15.