In 2009 an abandoned subway chamber was opened so 103 artists could paint, getting one night each. it was to take away the commercialism that a lot of street art had become. I thought this whole idea was amazing. Afterwards the chamber was sealed up, it could be discovered by later generations or just left to decay (which I think in itself would be pretty great).
I've also found the work of Michael Eastman, a photographer who travelled across America for documenting the many 'ghost towns' or places that once boomed with trade, and now stand, left to rust.
http://weburbanist.com/2010/11/24/under-the-city-street-art-peels-back-urban-layers/ - also for A-mazing camouflage street Art.