Mini-Golf on the Roof!

Yes, this house in Igualada, Spain has a mini-golf course on its roof. A mini-golf course on its roof! Is it useful? I could point out the efficient use of space, especially as the same shapes provide equally interesting interior ceiling features and golf course obstacles; I could speculate that the turf covering is extra insulation, and probably deflects heat; I could worry that noise from golfers might distract inhabitants inside... But really, I just want to say: it's a mini-golf course, on the roof!
[via Gizmodo]