Antibes is a fairly smallish place with Picasso museum overlooking the ocean. There is a cute covered city square and some medieval streets with little restaurants. There is a small beach - actually one small beach between the harbor and the stony cliffs, and then another larger beach. There is also a city wall as I recall and on the other side a harbor. One time I was there, there was one of the largest yachts in the world 400 ft long owned by some middle eastern king or prince.
Nice is not bad at all. I have been there 4 times. It's a much larger place with long slightly curving stone beach, with a very nice and big promenade, where you see some people jogging or whatever. The beach - being stones - is not all that comfortable but people still go and lie on it. There are some various little districts with restaurants and shops. If you walk all the way down the beach, it goes up a hill and around a corner. From that vantage point you can get some good pictures. If you continue around the corner there is a large harbor where you can take a ferry to Corsica or Genoa or whatever.
Cassis is the smallest but most picturesque of the three.
There is also Cannes (a little too posh), Beaulieu Sur Mer (pleasant seaside town at the foot of the corniches), Villefranche-sur-Mer, Menton, San Tropez (made famous by Brigitte Bardot's movie), Saint-Raphaël / Frejus, Cap Ferat (estates for the super rich), Eze (hard to reach tourist attraction), Toulon (a bit gritty with some no-go areas - one of the main ports of the French navy), etc.
None of them are bad places. But to me - they are France but they lack being obviously French or having much history or historical charm. They are essentially nice beach towns - which attract various foreigners for beach fun, and were the living spaces for various famous painters (along with Arles, Aix-en-Provence, etc.). Indeed, the father of modern Italy, Garibaldi, was born in Nice which it was more apart of the Holy Roman Empire or Liguria or whatever. It's ironic and that Nice and Mention are now French.
Much of the rest of France has 1000 year old churches and abbeys, 700 year old castles, long culinary and/or wine local cuisine, half timbered homes (500+ years old?), sites of WWI, WWII, Roman or Napoleonic battles.
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