A registration rule, not a size rule
Article 9 of the municipal order of 27 February 2007 says this: unless a special waiver is issued by the town hall, access to Monaco-Ville is forbidden to all vehicles except those registered in the Principality or in the Alpes-Maritimes.
Read that twice. It says nothing about length, height or weight. It talks about the number plate. A car chartered in Paris, in Marseille or in Italy does not go up to the Rock, and taking a smaller vehicle changes nothing. It is the only access rule on this coast that turns on registration, and it is exactly the sort of thing you find out too late if nobody says it.
The same article frames the rest: deliveries are limited to the 7 am to 10 am window, and motorcycles are banned from 10 pm to 7 am unless electric. Further on, article 2 sets the general limits: beyond 18.75 metres long, 2.60 metres wide or 4.30 metres high, a vehicle may not circulate anywhere in the Principality.
Six metres in Fontvieille, and the heliport behind the stadium
Article 13 creates a one-way system from quai Jean-Charles Rey towards avenue des Papalins. On that road, vehicles longer than 6 metres are banned, as are those whose gross weight exceeds 7.5 tonnes.
This is the road serving the port of Fontvieille, a short distance from the heliport. A sedan fits. A short van fits. A seven-metre minibus does not. That is why the vehicle is chosen when you book, against the address, and not only against the number of passengers.
The heliport itself is an easy landmark to give: avenue des Ligures, behind the Stade Louis II. The Monegasque public service adds that most international flights leaving Nice airport can be checked in there.
Three motorway exits, three different ways in
Exits 56 and 57 lead onto the A500, which runs in tunnel before rejoining the D6007, and serve the southern districts: the Rock, Fontvieille, Port Hercule, Monte-Carlo. Exit 58, signed Beausoleil, comes in from the north, on the Larvotto side.
Taking the wrong exit means crossing Monaco again, which is expensive in time where tunnels and one-way streets offer no second chance. So the choice is made in advance, against the exact address, and it changes with the hour and with the racing calendar.
If the trip has to be short and certain, there is an honest alternative: the helicopter link quotes seven minutes of flight, a departure every thirty minutes and 195 € per person, with a last flight before nightfall. The rest of the day, the road takes over again.