Actually Harold, it can rather be fun to contemplate various routes in Monaco and see how short and easy they can be on foot.
I agree that the buses, fast, frequent, cheap and go everywhere with a possible change (only 6 routes) are pretty much a fun trip too.
Without consulting a map, I want to see if I can remember.... OK, Aquarium to car park, down something like 15 floors to either zero or +1, marked Pecheurs.
Short walk to the inner harbour where the biggest yachts dock. Electric boat across the harbour. Walk diagonally towards St Devote, stopping for an ice cream just before the entrance to the Travelator (moving sidewalk). On there either one or two segments, elevator up about 5 floors. Cross the street and walk half a block. Escalator down 2 flights, around the corner to Cafe de Paris, Casino on the right hand side.
Now I've never made that precise walk and it may not be perfect, but I don't think it is off by much. Up and over and down to avoid walking up the fairly steep hill between St Devote and the Casino back door. I'm sure that if you stay on the marina side and don't go up the hill there is a sequence of two elevators which get you to the back door of the Casino, but I prefer the other route because I get an ice cream (right next to the yacht dealer)..