The map above shows the layout of the main sewer system of Adelfarn. All of the main conduits are shown, but the many pipes and bricked off chambers have not been displayed. The corresponding layout of the surface structures is overlaid on the map, and many of the sealed subterranean chambers line up closely with these walls. Since the sewer system of Adelfarn was originally built many centuries ago, it has been extensively modified and even completely rebuilt in places. As a result in many ways the passages are laid out like a maze, and the myriad passages can prove disorienting.
The sewer tunnels consist of a branching network of vaulted brick or stone passages lying more than thirty feet beneath the town streets, and serving much of Adelfarn. The floor of these passages include narrow stone walkways and a wide channel meant to carry normal effluent and the accompanying wastes. The sewer tunnels slope gently downward until they join up at larger junctions that contain an overflow pool designed to collect excess water from floods. These are shown in blue on the map above.
There are three general types of passages in the upper sewers. These consists of the main junctions, the feeder tunnels, and the side passages. Almost all of the tunnels have reinforced masonry walls with an arched ceiling and buttressing columns every five to ten meters. The main junction passages are wide enough to require a row of columns down the center to support the double-arched ceiling. Both the main junctions and the feeder tunnels have walk ways on either side, while the side passages only have one. In selected locations there are raised side chambers where the sewer workers can stow their cleaning equipment and take a rest from their labors.
Pipes entering the tunnels from above are covered by an iron grille at either end to prevent accidents. Sewer work entrances are built into the sides of street walls, and most have a flight of steep stone steps leading down in a gentle spiral. However, generations of sewer workers have worn down these steps and they are often covered in muck, slime, and moisture, making the descent somewhat hazardous.
Over time the sewers build up so much muck that they need to be thoroughly cleaned to prevent blockages and floods. At these times the town council hires outsiders to bring in various large scavengers and slimes to give the passages a proper cleaning. When the work is done many years later, the sewer-dwelling denizens are then cleared out by teams of hired hunters wielding oil pots. Unfortunately these attempts to clear the sewers of these denizens are not always entirely successful, and the sewers have become home to some very unwholesome creatures. In addition there are the usual vermin, including rats and other rodents, who establish nests throughout the sewers and in the bricked off side chambers.