With less than 40,000 inhabitants at the ocean surrounded by France one can find the little country of Monaco. The only country smaller than Monaco is Vatican City! We visited this small country in March 2023 while staying in South of France.
Monaco is easy to get to if you are already in France, or even from Italy. There is a very good train connection from bigger cities like Nice and Cannes.
The first place we visited was obviously the famous Monte Carlo casino. Being there with a 2 year old means you cannot enter any casino of course, but we are no gamblers anyway. We tried to walk in on a picture, but that was only for the photo ;-).
Walking up towards the oceanographic, you see a stunning view of Monaco from a far. You will pass a lot of nice restaurants located at the water.
The Oceanographic has an amazing view over Monaco, and it is close to the Place du Palais. Also Jardin Saint Martin is located right next to the Oceanographic. From both the gardens and the aquarium, you got amazing views on the ocean. In the aquarium is a big room with projectors which is awesome for kids!