The Sewers

You reach the edge of the district where the river meets the slums. Below is a low stone embankment. Half-hidden behind that, and piles of garbage, and broken crates, is a large rusted iron grate. An entrance to the Blackwater Sewers. You descend stone stairs and feel a waft of cool, unpleasant-smelling air come from the sewers. From a cursory look, it's obvious that part of the sewer gate can be removed, as it appears to have been cut out near the bottom previously.

Perhaps there's something inside there. Amidst the muck, grime, and other things.