The Fuurin love hotel is an abandoned hotel that's been left to decay for the last two decades. Unfortunately, it's in Chiba, about 33 miles out due east of Tokyo proper(an hour and a half drive.) Maybe that'll strike your fancy if you like exploring unsafe buildings.
Unfortunately I don't know many myself, and Fuurin is the only one I couldn't even determine if it had been demolished yet or not. All the other ones that would be interesting like the capsule tower or Dreamland seemed to have been demolished already.