According to Frank, the Door causes a curve in space-time. I don't know exactly what that means, but he tried to explain it by drawing a picture of a mattress with different weights on it. A marble hardly affects the surface at all, but a bowling ball bends it quite a bit. He says that the Door goes so far that the hole comes out somewhere else (in the basement?). With the info we have now, there's no way to predict where the other end of the tunnel created ends up. Of course there's the opinion that it doesn't go far...at least not in the standard three dimensions, rather in the fourth: time.
Where ever the Door connects to, it's certainly keeping Tom busy.
I think I've found some guinea pigs to send out to explore. If they get back to me soon enough, I'll have info to post next week. See you then.