It's the famous Tokyo 109 building (named after io9 of course), now falling into the same eco-ruins that overtook Manhattan in plague wipeout movie I Am Legend. In fact, Tokyo Fantasy has posted a whole series of images that all feature Tokyo in a post-apocalyptic state which manages to look rather lovely due to all the lush greenery. Reminds me of the abandoned amusement park in Miyazaki Hayao's anime Spirited Away. More green doom below.
Here you can see an industrial area slowly breaking down into nothing. And I love the two images below, which show the greening of a shopping area as it slowly goes back to nature.
Images of the Apocalypse [via Pink Tentacle]