A beautifully done interpretation of the Slytherin dorms.
The pool of water/ceiling light is based on the idea of an aristocratic Roman impluvium/compluvium. Gryffindor has a furnace in the center of the dorm rooms, so it seemed like an nice yin-yang effect as Gryffindor=fire and Slytherin=water. I’m not sure if the compluvium would magically let rainwater (and snow, and hail!?) in from the lake above, or not. I think it should.