The Cloaca maxima is commonly known as a massive sewer system that stretched an enormous distance through Rome. While this is true, modern historians and archeologists claim that the Cloaca maxima served a different purpose, serving as a fresh water canal that transported water throughout the city during the times of Roman Kings. When Rome’s population began to increase, a method for draining sewage, draining marshlands around the Tiber River, and preventing flooding within the city, especially in large public areas like the Forum Romanum. Thus the Cloaca was later to facilitate these purposes, and underwent numerous modifications throughout Rome’s history. Just as many ancient structures do, the Cloaca is in danger of collapse in some areas, but the sophistication of its architecture and function can still be seen today.
Smithsonian Channel video: https://www.youtube.com/watch?v=5cLGhXLoohM