You Can't Go There Anymore was a title of a zine my friend Extrovert Kurt (a big fan of urban exploration, like myself) wanted to do once upon a time. He'd take pictures of abandoned old buildings that were going to be demolished, and then publish them once they were gone.
Some places which once existed that you can't go to anymore include Phoenixville Steel Mill, Beach Pneumatic Subway, Hunter's Brook Bridge and now---under more tragic circumstances---the World Trade Center is also in this category.
(If you hurry, you can still see Centralia and King's College, before they disappear.)