This is some thinking I've made
Okay, so island nation (now known as Caelifer) is going to be the center of the roleplay, for now, I recommend changing the name of Sevii island for something that isn't taken out of pokemon, but oh well
What is the size of the city? I'm going ahead and suppose that weather of UM is bullshit, because a continent that close to the ecuador would be a permanent summer, and we rather have a moderate weather to work with of humid subtropical or mediterranean. When I imagined Academia city the closest in a real world counterpart that comes to my mind is
Santa Cruz, California but I'm going ahead and suppose that the Academia itself inside the city is as big as as another city, with half million students ranging from elementary all the way to university studies. It might seem massive, but we have said that Academia city is the number one when it comes to studies. Entrance is not completely restricted, a potential student gains bonuses for entrance based mostly in a passing exam and the entrance grade required is lowered depending on factors such as the residency, allowance, integration, if it has studied previously on the academy, etc.
So about the academia, you mentioned the library, of course, but what are the most important buildings? I suppose a main hall, a building for elementary students, two or three buildings for high school students, and a bunch of faculties for things such as law, engineering, liberal arts, mathematics, magic, medicine,sciences, etc. All of them with a main building surrounded by enormous pavilions that specify the study (criminal law, weapon development, history, physics, pharmacy, etc.). Not to mention the possible student and staff residences and shops and restaurants.