"So I read long ago, the founders of the school brought together their favourite parts
of their favourite building to make the school, hence why it looks like a big patchwork quilt Enjoy!" - Vasu Nivan The Archivist, Librarian
The School itself is floating over Iceland. The school does not float there by itself the grounds that surround it are there as well, it's somewhat like a floating island. The island has stayed hidden from those who are ignorant of magic since it was founded by magic means.
A large blimp brings the students to the school during the year, there are also other ways to leave the Island, brooms for example.
The school has been said to look like a giant peace of quilt work. Rooms that look like they have been taken from all over the world are together walking through a door could lead to a totally new form of architecture. Given the types of rooms it would seem the original founders where not the only ones to add rooms.
The Main school is it's own large sprawling building. Off in a separate set of buildings are the dorms, four long buildings that are pairall to one another and close to the school, the two center buildings are the longest one for the boys dorms the other for the girls, on the opposite sides of the general student dorms are smaller dorms one for the teachers, the other for the student council.
Floor One of the Main School Contains rooms commonly used by all the students, The dinning hall, the common room, The Library, the Office for the Student Council, The Kitchen and a rather extensive broom closet.
Second floor is all classrooms of different shapes and sizes. Each Classroom has a small office for the teacher connected to it.
Third Floor is the teachers general rooms, the staff lounge, the headmaster's office. The Owlry, and most likely other things I haven't thought of yet.
Below the basement are the catacombs, it's doubted that anyone except for the teachers and maybe the student council knows what is down there, this are is generally off limits.
The Ground outside the school include a large court yard, a large sports field, extensive gardens maintained by the students. There is also a forest and a waterfall students are forbidden to venture past the marked trees. first years are required to stay out of the woods all together.