CaviRio were great at communicating with us, both prior to our stay and once we were there (sending us suggestions of places to go to, etc). The flat was very well situated, and felt safe. The only frustrating thing was that the flat's decoration and furniture were more run-down than in the pictures... Though to be honest, we had so much to do in Rio that we spend most of our time outside!
All in all, we would recommend staying with them yes x