Wanted to share my experience on return a car in Caen on Sunday.
We knew that Caen was going to be closed on sunday, and there would be a dropbox. We get to Caen and there doesn't seem to be any parking lot for rental cars. At least none that I was able to locate. I circle a couple of times and ended up parking on a spot about 200 ft away. It seems weird, but I couldn't think of another option. I wrote a little note on where the car was parked and dropped the keys off. Its been 2 weeks now, and no additional charges. I guess that seems to have worked.