We were walking through the historical plantagenate part of le mans before going back to our hotel. it was a warm night, no precipitation with a little high cloud. both of us looked up at above the rooftop in front of us. we saw a very bright blue green spherical object with what looked like a short flame exhaust. it travelled slowly from left to right, what looked like a few feet above the roof tops. there was no sound and we both felt very calm and a bit fascinated. it continued in a straight line for 1 to 2 minutes and then just vanished. there was no vapour trail or anything throughout and nothing when it vanished.