"It does-- for as long as it stands. And it's good to have something of the outside here, against the order of the walls."

This is not said with any particular sarcasm, though Harry might think that the place has very little evidence of order. But there are totally straight lines still visible in places!

"It's good on nights when the ceilings here are too strange, too. Jehan's idea, so of course it works; he understands about dreams better."