"Anywhere, I would think." He was excited now, as well, that she was practically saying yes. "Empty classroom, Take over a hallway, outside of the Slytherin Common Room so that when they come out, all they see is fort." He was joking about the last bit. They could leave messages in the journals for all the single people who wanted to come out to come and find the fort also, so that they didn't have to wander around alone, or be stuck in the dorms.