The History Channel has a series called "Life After Man" or some such, and they show how the planet tries to repair mankind's presence after mankind stops using locations. Look at where America's train tracks used to be - nature reclaims the pathways, though some towns/cities use the old track beds for hiking and biking.
Remember Mowgli in "The Jungle Book?" After the village elders mess with his Mama, he decides that they are evil, and 'lets the jungle in,' and the village becomes like the Lost City - gone!
