Oh, I don't know... There's this model that Wataru Itou of Japan spent four years building, and it has lights, a train, and fills up a whole room... It can be seen here:
A Paper Craft Castle on the Ocean
That would qualify as the ultimate paper model, to me.
I would nominate my own 1/200 Montana-class Battleship, but the plans and kit aren't anywhere close to being finished.