- The First Sewer is opened by the Small Silver Key.
- The Second Sewer is opened by the Tall Key.
- The Third Sewer is opened by the Grande Key.
- The Fourth Sewer is opened by the Mayor on the final day of the Second City Adventures.
You can find several nifty prizes, fight random NPC battles, and continue your adventure inside the sewers. The mini-map is normally covered, unless you find the map for that sewer (incidentally, in that sewer).
Moving in the sewers requires being alive and costs 2T. Equipping the Gas Mask won through the Bowling Alley reduces movement cost to 1T, and protects you from various traps randomly located in the sewers.
Some unique items and objects can be found inside the sewers. The Mirror Shard can be found inside Sewer 2. The Space Rat can be found in Sewer 4.