Every so often, someone talks to me at a show and says something along the lines of "I don't understand why you people don't built your layouts on doors. They would be excellent.". They usually expound on the idea telling me that second hand doors are cheap, ready made and wooden. Apparently all these are desirable attributes for a model railway baseboard.
My reply usually involves pointing out that as far as I am concerned, plywood is much better. Doors are heavy, thick enough to make fitting point motors impossible, have no where to hide the wiring and most importantly, not made of wood. Unless you consider two skins of hardboard separated with pine spacers to be wood. Real wood doors tend to be paneled and thus provide a truly rubbish base for track what unless you want to base your model on a particularly dull roller coaster or perhaps the Docklands Light Railway. Oh and because they are door sized, difficult to get through normal doorways.
Apart from that they are perfect.
Not to be detered, Keith Bristow has made a railway on a door. It's quite nice too with a continuous run track plan - admitedly this requires very tight curves - and sidings and loops just like a proper train set. There's quite a bit of scenery and a couple of buildings. That bus should be on a bridge really (it's a model railway tradition) but if you were looking for something for your kids, it's got a lot going for it. I'd have been quite happy with it when I was a kid. You can run trains around and shunt, more than the majority of proper, grown-up model railway layouts can offer !