"Mr. Weasley, aren't we still underground?"
-- Harry Potter as they passed a window on Level 2 through which sunlight was streaming (OP7)
This map is very much simplified from what is undoubtedly a very large level with many offices. Harry and Mr Weasley leave the lift and walk down a corridor with many doors on one side and magical windows on the other. Then they pass through Auror Headquarters (an experience which likely influences his desire to become an Auror himself one day) and from there through to the small space where Arthur shares a tiny office with Perkins.