First place to visit what is free, is the sea, is very beautiful it has 3 colours in it, the water is clean and is healthy to breath some salt from the sea, you have free beaches and also the ones where you have to pay, this is what i like about Nice, you always have an option.
Second free place to visit is Old Town of course, very beautiful, you can hear the life music while you are walking around, you can grab scream, it will take you a while until you chose from 100 different taste, but you have to try them, they really tasty.
Another place is the Castle in front of the sea, they you go up, yo can go by stairs or you can go by the lift, is very hight, but the few is magical, there you have waterfall as well, very beautiful, also there is one restaurant and playground for children, but i go there, for the view, is breath taking.
The docs of Nice, if you are fan bouts and lots, you should definitely have a look, is huge and interesting, you can see many bug fishes around them, but is forbidden to do fishing in there.
The magical Coulee Vert garden is very big garden at first part you have many playgrounds, flowers flowering trees, at second part you can do pick pink, after is my favourite, is FONTAINE big i just have to shoe you, because i don’t have enough words to tell you how cool is this.