Gender, but do not quote me.
I think the answer to the gender question is that Le Belle Rive is masculine because it is a hotel (masculine). A feminine noun which is an adjunct of a masculine noun loses its female gender. For example the area 'the Camargue' is feminine ie. la Camargue. BUT if a boat (masculine) is given the name la Camargue it becomes Le Camargue! I was on the boat 'Le Camargue' looking at a map which called the area 'La Camargue', so I asked a French man who gave me this answer. BUT don't quote me on this - I could have been a hapless tourist who got conned.
Peter Caborn.