This set is made to have sewer runs and have fun while doing it. The sewer comes with pipes, pump stations, and even valves. You have rooms that you can put just about anywhere and connect them if you want to. You also have a ladder and crosswalks to place throughout the dungeon if you want to make a multi-level sewer system.
Sewer tunnels must be laid down first with the edges overlapping because of the blurred edge to give as close as a smooth transition as possible. There may not be a perfect seam but you can use objects to help hide the lines.
The walls/rooms needs to be laid down on top of the sewer tunnels with the open section lay just over the sewer tunnel walls in order to get them to transition smoothly.
Pipes and ladders and any extras must be laid down after the walls and sewer tunnels to see them. You may add rooms from another set to the sewer tunnels but be advised that not all rooms will mesh nicely with tunnels. After all there are few if not any doors in a sewer.