The Entrance Hall. Place of entry. Huge imposing doors that let you into and out of the castle. And four massive hourglasses on the wall filled with gems to represent the house points. Totally fancy.

The Great Hall. A hall of greatness. Feast your eyes on the enchanted ceiling and your stomachs on the five cauldron grub at mealtimes. Nom nom.

A classroom where people learn how to turn things into other things. Shame we can't transfigure this classroom into a party room or something more fun and less braining.

A room for the staff to do naughty, naughty things away from prying student eyes.