Despite Celestia’s dislike of the Upper class ponies snobbery, Canterlot was still a product of the Unicorn masons of its time. Therefore, the city outside the palace is broken up into 3 main boroughs, or districts.
There’s the Upper District, home to the noble ponies, where the sun shines through every window (which the nobleponies take as a blessing from their solar princess), and the district all ponies must pass through to gain access to the palace. Because of Canterlot’s strategic mountain fortress construction, and Equestria’s general peaceful civility, the city is rarely invaded, and nobleponies feel safe despite living at the city’s entrance. Furthermore, because the Royal Guard’s barracks are located at the entrance to the city, this also makes the Upper District the safest of the three crime wise.
The Palace is at the highest point in the city, and adjacent to the Royal Gardens and parade grounds. Celestia’s school is located within, as well as the chambers of Princesses Celestia and Luna.
Lying behind the city is the Middle and Lower Districts. These are the more humble districts. The Middle District acting like any middle class housing in any city anywhere else. It does not enjoy the constant sunshine of the Upper District, but feels it more than the Lower District. It’s your average houses, with your average families, and has the average amount of crime that any average suburban area would see. The Middle District holds the Canterlot Library (frequented by Twilight Sparkle when she lived there), as well as other average perks one would find in your average middle income town.
The Lower District, however, is where the unfortunate poorer ponies live, the lower middle class and upper working class ponies. Many of the palace employees live here in government subsidized housing (Celestia would never let even the poorest of ponies live as beggars). However, this district, being closer to the shadowy side of the mountain upon which Canterlot rests, does not get much sunlight, and thus is more prone to crime than the other two districts. Many of Equestria’s Royal Guards were born from this district, as their families could not afford to send them to higher education.
some areas are sewage, some are industrial, some are recreational harems.
most train stations see no dailight.
The sewage systems has no drainage, thats why they build the garden extension.
But reading into things excessively is just part of this fandom (as well as any other).
Its still a fine theory of course, I’m just thinking you may be reading into things excessively.
Edited
Canterlot’s layout has always been confusing in the show, I agree. The CGI version is so much better in illustrating where everything is.
Those panning, zooming shots through it’s streets? Very helpful.
EDIT: Come to think of it, every wide shot so far* has always been from the front too, as if from the perspective of someone who’s never seen what’s actually behind Canterlot (most of the mane 6 but I expected with some degree that Twilight would have at least known about it). Even the maps only show the front face.
*until the trailer, but feel free to correct me
Edited because: see EDIT