The story begins a few hundred years after a plague and limited nuclear war decimated most of the planet. I don't want much knowledge to have remained, just myths and legends of a glorious past.
The question is - how long after a limited nuclear war (mostly targeting weapons sites, I guess) and a massive plague that emptied the cities would it take for the cities to be overgrown and crumbled to where there is essentially nothing left? Concrete has to crumble, metal to disintegrate. How many years?