Main Tunnels

You walk down one of the large pipes, pushing through the crowd. The pipes are fully round, with a river of brownish water flowing through the bottom. A wide grated metal walkway is built out about a third of the way up the sides and suspended with thick wiring from the high ceilings. Along the sides, an entire city has been built out of scraps of sheet metal and wood. It's a wonder it doesn't break, with the amount of weight it's supporting.