Well isn't that frustrating? You try to make your first ever tunnel, you have high hopes for this, it sees to be all lined up correctly, not too sure about the depths, but hey you can check those when you load the map in-game. So you save it, export it, load it, you see the tunnel entrance… you step into the tunnel… NNNNNOOOOO! You only see one section but u walk through and… huh?!? It's the next piece but you can't see other pieces - just blackness.