What the forget is that sewer
Ah the sewer, I guess that would be something to talk about.
The sewers will not be under the map. This creates complications of size, detail, too many bricks in one spot, etc. so rather it will be a different "area." You will teleport I to them, and they will not be to the same layout as the roads, mostly because I don't wanna copy that layout, but also because it's more fun. There will be a lot of exits and entrances, even some enters le teleport pipes (think Mario.)
The sewers are large. It's a city, they have to be able to handle a lot of sewage.
That said, there is excess room, almost enough to fit a helicopter (hmm)
There will be underground lots
There will be cave attachments to it
Maybe if Vaux loves me enough mutalids (doubt it, probably too irrelevant, but let's be honest, "monster hunter" is a loving awesome job, especially with a Sword-Axe)
The only problem I have with the sewers is that there are a LOT of cross-support beams. That will be fixed by either large beams, or just fewer.
Also worth noting, that's a custom brick pack: squideey's with blank side and ramp textures.