This is a bit late, since the readalong has been safely out of the sewers for nearly a week, but I never claimed to be sensible in my timing.
First of all, a map of Valjean’s escape route that originates from Paris sewer museum:
This is helpful insofar as it places Valjean in relation to city itself, but doesn’t help to make any sense of all the side tunnels and whatever else he was supposed to avoid. Fortunately there are more specific maps of the same era:
(Under the cut for labeled map with specific locations mentioned in this chapter: there will be another post with more sewer museum resources.)