Mentioned in the commentary is some pretty cool stuff.
If I recall correctly in the Archives Level, they actually do mention what i3670 said about there being a larger one, but I am pretty sure it was that the Archives level would be the start of A:TDD.
It may have also been the Archives, but there was another level which had to be rearranged quite a number of times as well. Whether it was scrapped or not, I do not remember entirely, but I assume you now have the final result of the level design in the game