Several people have been kind enough to send me a link to this video of a HUGE model railway. Though millions have already seen it, I think it's appropriate to post it again here in the name of completeness. So, just in case you somehow missed it, prepare to be amazed by The Wunderland.
From the video description:
The Miniatur Wunderland Hamburg, the largest model railway in the world, and one of the most successful tourist attractions in Germany. On the 1,300 square meter layout, more than a thousand trains, aircraft, cars and ships move about. A wonder of the world in miniature.
The Miniatur Wunderland includes an incredible level of detail. There are entire sections of the model that depict an airport, Switzerland, Scandinavia, America, Germany, Austria, and various regions in the Alps. Plans to add sections depicting Italy and France are underway.
Believe it or not, this is a model and NOT a photograph of an actual airport. Incredible.
You can find a lot more information at http://www.miniatur-wunderland.com. Readers of The Automata Blog might also be interested in the English section of their forum that deals with various aspects of model building and The Wunderland itself.
[ Thanks to Charles, Jarva, and others! ]