Matilda loves her cardboard A-frame “Playframe” house – she spends just about every day in there, up on the 2nd floor. I think she likes the position of the house as well – it’s at the far side of the room, so she has a view out over the whole room and can see us coming (though she often sleeps so deeply that we can walk right up to her and she doesn’t wake up).
Chuck sometimes comes for a visit, but he generally stays on the bottom floor – which is just as well; I don’t think both of them could fit upstairs!