turning a box into a playhouse

I got a tall sturdy box at work today - and am planning to make it into a playhouse for Esme. It is hiding in the spare room right now. I'll have to sneak it up to Grandma's house after it is finished. I plan for Esme not to see it until it is ready, and/or until her birthday 'party' I'm thinking just to use a box knife to put a window, "working" doors and a little decoration on it so that it looks like a 'house'. Then she can put on puppet performances on one side and/or play 'house' on the other side. I don't know how long it will last - but that big empty box just cried out to be made into something for her :)