All...<br/><br/>Dasha pointed out that there is some confusion regarding what level of the base goes where and drew me a pretty picture that wasn't quite right.<br/><br/>I have shamelessly plagiarised her idea and here is the corrected diagram.<br/><br/>Please note: The height of the blobs is the only thing that matters. The width is irrelevant.<br/><br/>(http://elliquiy.com/elluiki/images/b/be/Levels.png)<br/><br/>So, the purple bars represent the connecting corridors. The orange levels are the life support levels. The red line is the surface.<br/><br/>Please forgive me for not mentioning the life support level on the habitat module description. It was the first one I did and I was still building the place in my head...<br/><br/>Hope that makes things  clearer? I will be editing the picture into the relevant post at the beginning.