Classroom 1B[1] (also known as the Transfiguration Classroom) is where Transfiguration class is taught. The classroom is located on the ground floor around the Middle Courtyard. The classroom itself is big, surrounded by high windows, has four rows of three desks, and still has enough room for several cages and bookshelves, two chalkboards, and a desk for Professor McGonagall. Several candlesticks stand lit behind McGonagall's desk.
In the first two film adaptations, the classroom is shown to be on the south side of the Middle Courtyard.But in Prisoner of Azkaban and the subsequent film adaptations, it is moved to the east side of the courtyard, since the former building is replaced by the Dark and Astronomy Towers.
In the first two film adaptations, the classroom 1B is actually the Chapter House of Durham Cathedral