Where do Kendra and Seth sleep while visiting their grandparent's home in the novel, Fablehaven?

Kendra and Seth sleep in the attic while visiting their grandparents. The attic is filled with things for the two of them to do, and Grandpa leaves them clues that lead Kendra to find out about the power of the milk. The attic room where Kendra and Seth sleep is only half of the attic, and the other half is filled with things used on the Preserve. The attic has an extra layer of protection which is only in effect when children are in the room, which is why Grandpa has them sleep there. He also tells them they will be forced to stay in that room if they disobey, but Seth disregards the warning and disobeys.