Ladders feature a bit in this show.
When we were at Art Melbourne a man had painted a number of things going on in the sky and this might have been my initial inspiration. However, stories such as Narnia where transition points occur in unusual places also spring to mind and I think I can vaguely recall a science fiction title like that. None of that need have any relevance here as the story so far is untold. I hope it suggests all kinds of possibilities.