Enchanted Ceiling

The Enchanted Ceiling is the high ceiling that covers the huge Great Hall of Hogwarts School of Witchcraft and Wizardry. The Enchanted Ceiling is bewitched to look like the sky outside and to mirror the weather. It is said that the mimicry of the sky outside is so exact that, at first glance, one would believe that there is no ceiling at all and that the hall simply opens upon the heavens.

In her first year, Hermione Granger mentions to her classmate Susan Bones that the ceiling is, in fact, bewitched and that she read about it in Hogwarts: A History.

There is also an Enchanted Ceiling in Classroom Eleven, the classroom that was converted to resemble the forest while Firenze was teaching Divination, but unlike the Great Hall, it was only enchanted to show the night sky, rather than the current weather.

The ceiling of the Atrium at the Ministry of Magic also seems to be enchanted to resemble the sky outside. Golden symbols continually move across it "like some enormous  heavenly noticeboard"; it appears peacock blue early in the morning and dark blue in the evening.