Passage of Time

For the land art idea, I think it would be kinda cool if you made a living family tree, but this would involve the entire neighborhood. For instance, you could use the side of a store, you know the huge canvas that usually has a mural painted on it, only instead of a mural, we would start off by growing a vine. Eventually that vine would grow and cover the wall and all the while, people can add snippets of paper (which would last and fade and eventually crumble away) with names and dates on them.