Potions classes are held in a dungeon classroom, large enough to hold at last twenty students, their cauldrons, and their work tables.
The classroom is quite cold, especially in the winter, when students can see their breath. There are pickled animals in glass jars along the walls (PS8). There is a basin in the corner of the classroom into which icy cold water pours from a gargoyle’s mouth. A student supply cupboard is in the room, along with a blackboard on which the instructor can write directions for student work (OP12).
Snape’s office and personal stores are adjacent to the Potions classroom (CS11).
When Snape becomes the Defense Against the Dark Arts teacher, he brings the same gloomy atmosphere with him to his new classroom (HBP9). -BB