There are several switches that must be found to progress through the built-in sewage system and hazards like spike traps as well as various Bandirats.
There are two lifts that ascend and descend to access parts of the sewer as well as an open pipe section that connects the map, requiring minor platforming. Close to the end is a section with moving platforms over a pit of sewage that must be navigated.
There some side areas with chests and some wall sockets dotted around that each contain one Carbon Steel Bar. At the end of the exploration section are several chests, one of which contains the Enhanced Iron Sword recipe book.
Before defeating the Rat King, if you die once, then you have the option to exit. You can exit and re-enter unlimited times. Once you re-enter, instead of turning left to where Rat King is, go to the right and open the three treasure chests for unlimited nitra, data disc, power stone, and enhanced iron sword recipe (50G).
After a fight with the Rat King the pollution flow can be shut off at a valve.