My latest layout isn't the only pizza that I've built, nor does it push the boundaries of what's possible in four squre feet. Several years ago I used the same two by two footprint for a finescale OO gauge layout. Like my current narrow gauge project it was aimed at an exhibition audience; the similarities also encompassing punter push button operation. Obviously only short wheelbase stock was comfortable with the ten inch curves on the main line (the sidings being purely decorative) but even the six wheels of my 03 and 04 shunters made it round the corners. The limiting factor was actually the three link couplings, which to stop buffer locking had to be temporarily lengthened to four links. Anyway here are some photos and trackplan of the layout.
Though the layout is long gone there are a few remains. The buildings sit gathering dust on one of my playroom shelves waiting till I find a use for them, and somewhere I have the point and crossing formation though I seriously doubt I'll ever manage to recycle it into any layout.