was the greenhouse-like roof rooms attached to the top level apartments (via internal staircases). Apparently they're too cold in winter and too hot in summer to really be used for anything except keeping gardening tools, which is not too surprising as they're all glass.
The location is 5 minutes walk from the shops, 8 minutes from the train station, 1 stop to Rennes then 1.5 hour TGV to Paris.