I have begun work on the monster! I cut out some floors for the quadrants. I am 70% sure I shall be going with the external lift-shaft suggested by Porky, but for now I am just omitting one of the quadrants, so I retain the option of having an internal one. The floors are made from a layer of 5mm-thick foamcard. I then cut a layer of 0.5mm-thick plasticard, and scored half-inch squares in it to give the impression of a tiled floor. I cut through some squares, suggesting that whatever has happened to the building, some of the tiles have been broken and dislodged. I cut a few doors from 0.5mm-thick plasticard: 2" by 1.5". I laminated two pieces, cutting a hole in the middle of one, giving the impression of a door-frame around a sliding door. I have glued several of the upper floors in place. I was a little worried, having done so, that it could prove difficult to move models around when they are close to the middle, but this proved not to be the case.
Recently I have been trying out this idea of inserting pictures into the text, but it hasn't been going so well. Everything looks fine when I type the post up, but once it's published, I realise the system just hates me. So in future tutorials I shall be going back to labelling things with numbers. For now I'm just going to throw a load of pictures at you. They're pretty self-explanatory, and this isn't a tutorial, so no need to worry. Keep your eyes peeled for a tutorial in a few months!