All Celebrity ships are too big to dock in the Port of Nice, so they actually mean anchoring off Villefranche. Look it up on a map. Absolutely beautiful. Get a tender to shore. You can DIY local bus/train to many interesting places if you don't want to walk around Villefranche. Trains are very cheap. I don't recommend the local bus serve at Villefranche these days, as they are full of people to/from Monte Carlo all the time. But still very cheap if you want to do it. Trains are better but can still be very crowded. Corsica on Celebrity will probably be Ajaccio so you can DIY. Lovely town, full of history, beautiful scenery and good local food market 10 minutes from when you get off the ship, also Napoleon's birthplace nearby. Marseille for the Celebrity ships, unfortunately you will be at the new cruise port which is horrible and a long way from the heart of Marseille. DIY- if you know how - otherwise you need the ship shuttle into town. Marseille is truly interesting, however if you have never been to this region before, a trip to Aix-en-Provence or to the Luberon may be what would appeal to you more.