You begin making your way down the staircase. You move slowly and carefully as the steps beneath your feet feel a bit slippery. Just as you move out of sight of the entrance, the trapdoor slams shut above you. You return to the top of the stairs and find it will not open again no matter how hard you shove. You make your way downward, noticing small domed lights along the walls emitting light. The stairs get slicker the further you go, and you walk for a few minutes before finally reaching the bottom. The floor is made of stone and is covered in roughly a centimeter of water. You follow the passageway leading away from the staircase into a large round tunnel dozens of meters wide. The smell you noticed at the top progressively grew stronger as you made your way down, and here at the bottom the stench is almost unbearable. You can see why - you are apparently standing in a sewer. A moat of foul, murky liquid flows along the bottom of the tunnel. Walkways line both sides with more of the small, domed lights lining the walls beside them. The passageway you stand in opens up to a walkway on one side of the tunnel. The tunnel seems to be curved and slanted, with the left side elevated and the right side curving slightly downward. You can follow the walkway upwards to your left, follow it downwards to your right, or you can give your flashlight or whistle a try.