Alright, fair enough! Allow me to give a basic run-down of Septum!
Septum's core is obviously the location of where the Church is at (the direct center). Surrounding the church is a smallish round park. Outside of this area, is where the city aspects of Septum come into play. Literally, skyscrapers, large hotels, chain-restaurants, suburbs, downtown area with shops and malls, movie theaters, etc., literally lots of stores and locations; although it seems as if its a little too perfect to have all of these with little to no crime happening. Septum itself is roughly... 100 sq miles are so.
Outside of Septum surrounds it a small plain of fields not that wide... maybe a few miles or so, until you come across the four major biomes. To the North, is the Arctic Tundra biome; the East is the Desert biome; the South is the Jungle/Amazon biome, and to the West is the Mountain/Lake biome. These biomes are rather large, each covering roughly 1/4 the size of Septum in itself. Each of these biomes are again separated by a mile or so of plains in the directions of North-East, South-East, South-West, and North-West. Animals native to these biomes, including extinct and endangered species are also present, but for some reason they don't seem to harm one another which is highly unusual.
So... in total, I'd say Septum, as a whole including everything, is roughly 200 sq miles, biomes and everything.
If you need more information or details, feel free to shoot me some more questions.
Edit: Also, there's a reason why I had the different biomes included into Septum; one reason is for more variety in fights (city fights can get boring), and it allows for creativity, while another reason is story-based and will be revealed later on as the game progresses~