The name Cloaca seems to be related to Cloacina, the Roman goddess who was believed to presided over the Cloaca Maxima.

Beyond its technical achievements, the Cloaca Maxima held significant cultural and symbolic value. The Romans viewed the movement of water as sacred, and thus the sewer may have had religious significance. Its age and enduring effectiveness further elevated its status as a symbol of Roman civilization and engineering prowess. Writers like Livy and Cassiodorus celebrated its excellence, with Livy noting that the drain's construction was unparalleled by the splendor of his own time. The Cloaca Maxima became a symbol of Roman superiority, with its continued function over centuries reinforcing the greatness of the Empire. British writer Henry James remarked that the drain gave him "the deepest and grimmest impression of antiquity I have ever received", underlining its awe-inspiring impact. The Cloaca Maxima's influence extended beyond Rome, with Roman sewer systems widely imitated throughout the Empire.

circa 600 BCE- Modern Period

Roman Kingdom Period
According to tradition, the Cloaca Maxima may have been initially constructed around 600 BCE under the orders of Rome's king, Tarquinius Priscus. He is said to have enlisted Etruscan workers and plebeians to construct the sewer system. Before the Cloaca Maxima was built, Priscus and his son, Tarquinius Superbus, undertook major land reclamation efforts to transform the marshy terrain of the Roman Forum into stable ground, thereby reclaiming the Velabrum. This was achieved by filling the area with an estimated 10,000–20,000 cubic meters of soil, gravel, and debris.

In its earliest form, the sewer consisted of open-air channels lined with bricks, centered around a main drainage pipe. It may not have had a roof initially, though the presence of wooden holes throughout the sewer suggests that wooden bridges or scaffolding could have been used in its construction. Some theories propose that the Cloaca Maxima may have originally functioned as an open drainage system, redirecting natural streams from three neighboring hills through the Forum and into the Tiber River. Over time, as space within the city became more valuable, the drain was gradually covered and integrated into the expanding urban infrastructure.

Roman Republic Period
By the late Roman Republic, the Cloaca Maxima had become the city's primary storm drainage system, extending to a total length of approximately 1,600 meters. By the second century BCE, a 101-meter-long canal was constructed and subsequently covered, further expanding the drainage system. Pliny the Elder, writing in the late first century CE, described the early Cloaca Maxima as being "large enough to allow the passage of a wagon loaded with hay".

As Rome's population grew, the sewer system struggled to keep pace with the city’s expansion. Romans often discarded waste through alternative openings rather than through the overburdened sewer network. From 31 BCE to 192 CE, manholes provided access to the sewer, allowing for maintenance and inspection. These manholes were sometimes adorned with marble reliefs, and the underground canals were constructed using Roman concrete and flint to ensure durability.

Roman Empire Period
By the first century CE, the Cloaca Maxima was integrated into Rome's sophisticated water management system. The eleven aqueducts supplying water to the city also funneled excess water into the sewers after it had served public baths such as the Baths of Diocletian and the Baths of Trajan, as well as fountains, imperial palaces, and private homes. This continuous flow of water helped flush the sewers and prevent blockages.

The Romans carefully allocated water resources: the highest-quality water was reserved for drinking, while secondary water sources were used for baths and fountains, with their outflows connected to the sewer network. The Cloaca Maxima remained well-maintained throughout the empire's history and, remarkably, still functions today, continuing to drain rainwater and debris from central Rome, including the ancient Forum, Velabrum, and Forum Boarium. In modern times, portions of the ancient sewer have been integrated into the contemporary sewage system to mitigate backwash from the Tiber River.

Medieval and Modern Use
After the fall of the Roman Empire, the Cloaca Maxima remained in use. In the 1600s CE, the Cardinal Chamberlain imposed a tax on Roman residents to fund its maintenance. By the 19th century CE, the sewer had become a popular tourist attraction. Between 1842 and 1852 CE, sections of the sewer were drained, leading to further archaeological and engineering interest.

In 1862 CE, Italian engineer Pietro Narducci was commissioned by the city of Rome to survey and restore sections of the Cloaca Maxima, particularly around the Forum and the Torre dei Conti. Later, in 1890 CE, German archaeologist Otto Ludwig Richter created a comprehensive map of the sewer system. These restoration efforts contributed to renewed public interest in sanitation and urban infrastructure, highlighting the lasting legacy of Rome's ancient engineering achievements.

circa 600 BCE- Modern Period

The Cloaca Maxima originated near the Forum Augustum, where it tapped into the natural landscape and followed the course of the ancient suburbs of Rome. This route wound its way between several prominent hills: the Quirinal, Viminal, and Esquiline Hills. From its starting point, the sewer passed by a series of significant locations in the heart of the city, including the Forum of Nerva, the Arch of Janus, and the Forum Boarium. As it continued its path, it also passed the Basilica Aemilia and the Forum Romanum, two key public spaces in the city. Ultimately, the sewer emptied into the Velabrum, a low-lying area that served as an important commercial and residential district.

The drain's outfall was situated near the Ponte Rotto and the Ponte Palatino, both of which are still visible today, offering a direct link between the ancient and modern city. Throughout its route, the Cloaca Maxima incorporated a network of branches, which served as "official" drains. These branches were integral to the city's sanitation system, specifically designed to channel waste from public toilets, bathhouses, and other civic structures. The drain's extensive reach underscores its importance not just as a drainage system but as a cornerstone of Rome's urban infrastructure, designed to support a growing metropolis and its public health needs.

circa 600 BCE- Modern Period

The Cloaca Maxima was an extraordinary feat of engineering, large enough for "wagons loaded with hay to pass" according to Strabo. It could transport up to one million pounds of waste, water, and unwanted goods, all of which were carried to the Tiber River. The sewer used gutters to collect rainwater, debris, and spillage, and its conduits dispensed up to ten cubic meters of water per second. The structure incorporated vaults closed with flat panels or rocks, and a trench wall was used to hold back sediments. Despite its immense capacity, some of its water remained polluted, contaminating water sources used for irrigation, swimming, bathing, and drinking. The sewer also served a practical function in controlling malaria by draining marshy areas and limiting mosquito breeding. In some instances, animals such as rats were able to enter the sewer system. The drain's ability to withstand centuries of use, including floods of filthy waters, has been praised by writers such as Pliny the Elder, who called it an engineering marvel. The system also served as a model for other Roman sewer networks, particularly in cities like Eboracum in Britannia (modern-day York).