Located adjacent to the Transfiguration Classroom door, is... well, another door. A small plague nailed to the front of the door reads;
The Transformation Room
When you enter, it might look like just an ordinary spare classroom. And... well... it probably is. There is no furniture here, only ample floor space, floor to ceiling windows with a view of the lovely Hogwarts Grounds, and a high ceiling. You can use this room to practice your spells or to complete homework.
At times, Professor York
might have transformed the room into something else. Keep checking the Noticeboard for any information.