The Sewer Network is one of those regions of Paragon City that, for some reason, people rarely visit. Perhaps it's due to the fact that the enemies are tightly packed and difficult to get around. Maybe it's because, with The Hollows, Kings Row, Perez Park, Atlas Park, and Galaxy City all sharing the same level range, there's too much competition. Maybe it's because it's a sewer network. Most people only pass through it on their way to the deeper Abandoned Sewer Network, for the Sewer Trial at level 36+.
If one should find themselves here, it'd be wise to bring a team, or you may find yourself committing suicide just to Mediport your way out again.