Written by BaltoSeppala :

Hey everyone!  Mightybalto1925, Matsu and I would like to thank you for your continued activity and contributions on Zootopia Source! 

Today I'm going to update you on our latest work-in-progress, the "style" (layout) for the Nocturnal District, and talk about influences, references, etc. 

Of course we all already know that, while there IS an official "Nocturnal District" listed in the Zootopia canon, it was never seen in the movie.  There are only references to it...and those are official references even made by Byron Howard and Richard Moore, two of the directors of the movie.  I've also seen vague descriptions or inferences about the district floating around the net, though there isn't much. 

So what do I envision the Noctural District to be (taking into account what has been described in the link above)?  I see a region of perpetual night...a long and extensive network of caves, caverns, tunnels and passages, extending for miles underneath the city proper (and being accessible from it), and into the outlying regions around the city...from the Canyonlands and into the mountainous regions that flank the city.  All of what I see in my mind's eye is based not only upon research into real underground environments, but also influences from my youth...back in the days when I played Advanced Dungeons & Dragons as a kid and teen, and read "The Hobbit" and "The Lord of the Rings", etc.  Though, rather unlike the descriptions of the "deep places of the Earth" in those stories and the AD&D game, my views of the Noctural District are based a bit more in the real world and, while it would be an ideal place for Zootopia's criminal element to hole up and conduct illicit activities, it is also a place where law-abiding citizens of the city also make their living...so there would obviously be legitimate neighborhoods and settings for the citizens to enjoy!

Let's look at some real-world influences and I can go into more detail about how we are planning the layout.

Of course, the overriding element of any underground setting is that of caves and caverns...some of them are huge (spanning a mile or more in diameter, and thousands of feet in height), and others are very small.  Some are wide, others are narrow.  Some contain deep chasms or seemingly endless holes that drop deep into the Earth.  They have fairly common features: stalactites and stalagmites, irregular rocky floors and walls, and sometimes creeks, streams or even lakes.  The floors, walls and ceilings are often (especially at the near-surface regions) covered in mosses and lichens, and even various fungi (mushrooms and such)...some of which give off bioluminescence in the dark...just as many of them do above ground.
 

Of course, in the deep, dark places of the world, not only plants and fungi give off bioluminescence, but animals as well!  There are plenty of photos of real worms, which populate the ceilings of caverns and passageways underground, which give off a natural blueish-green glow...they habitate in large (and sometimes vast) colonies, hanging from the ceilings and looking, from a short distance, like great starfields.  We are definitely going to be incorporating these into the layout appearance (as well as that of the mushrooms)! 
 

The other forms of life (besides the mammals) below ground would include a lot of different forms of worms (including gloworms), a ton of different kinds of insects and arachnids and, in the water you'd see blind cave fish, crabs, etc.  Each of these would doubtless serve as food items for the mammal citizens living in the district.

So what would the city environment look like?  Well here is where imagination most comes into play.  Would the citizens of the city carve buildings and homes right into the rock faces?  Or would they build structures in large cavern spaces?  How would they light it?  Would they run electrical wires and put up lights?  Or would they make use of the natural bioluminescence to save on electricity, and perhaps culture the worms and fungi (and other bioluminescent plant life) to help light buildings, passageways, etc.?  Personally, I think it'd be a combination of all of these.  Below (at the bottom of this news feature) are some pictures of art I got off the net (none of which belong to me or to us, and which I make no claim over) which perhaps can help establish that vision.  They are also not concept art from the movie, but were created by independent artists.

And since Byron Howard and Richard Moore indicated that the district also runs under the main above-ground city itself, surely there would also be several tunnels and structures, laid out with straight walls, floors and ceilings, which connect to subway routes, stairwells leading to the above-ground areas, etc.  And maybe there'd be access points just like in major cities for the subway systems.  Just like there'd be cave entrances in the Canyonlands, the mountains, and even seaside ones (each probably marked for easy access by the citizens of the city and surrounding regions).  This district would be populated by mammals who prefer dark and underground settings...bats, moles, gophers, rats (and other various kinds of rodents), badgers, etc.

These are all items we are using as references for developing the latest layout, and we think you're gonna love what we're coming up with!  (Especially those of you who love dark environments!  lol)  We fully hope this one will serve, in due time, as the default layout once the Halloween holiday rolls in!

So here (below) are those images to whet your whistle, and spark your imaginations!  And again, these do not belong to us, so don't go using them specifically for your art or fan fictions (always seek the artists/owners out for permission)!  Meanwhile, be watching!  We should release the Noctural District layout soon!

--BaltoSeppala