The Cloaca Maxima, emptying into the Tiber river, was the first Roman sewer to be built. Photograph courtesy of Leo Curran and Maecenas.org.

Here is a view of the Cloaca Maxima with the Tiber at full flood, when the cloaca's egress is almost completely hidden. The round temple on the heights above was once believed to be dedicated to Vesta but is now known as the Temple of Hercules Victor. Image courtesy of Franz Reubel and VRoma.org.