I honestly don't know about under the bed. I think it is probably boxed. I usually check to see if we've forgotten any socks or stuff under there and I don't remember seeing anything interesting. However, there is a nook area as soon as you walk in the door, oppositive the bathroom, beside the closet, where you could put the mattress during the day. It is almost long enough to lay it down flat but not quite. It would be a good place for a little one to sleep on a little air mattress though.