Ah! Then it is an extension of sorts, like when one creates a trunk, or indeed a house, that is larger on the inside than the outside. That is excellent! It is quite common in our magical system. I must ask, if the space is only anchored to a doorway, is there a risk of it collapsing in upon itself? If you were to create it and then to die leave? Or is it a working that outlasts its caster?