Most people go to Monaco from Nice, France like I did, which I think this could probably the best and easiest way to get to Monaco. It only takes around half an hour by train and I do recommend you to go. Most of my time there was walking up and down. And now I am going to tell you some sightseeing points that you can see a spectacular Monaco from top.
Jardins de Saint-Martin 98000 Monaco
Le Palais des Princes de Monaco 98015 Monaco
Jardin Exotique de Monaco 62 Boulevard du Jardin Exotique, 98000 Monaco
Huit & Demi 4 Rue Langle, 98000 La Condamine, Monaco
Another thing that I would like to share with all of you is the dish that I tried at lunch time when I was there. I randomly found this restaurant on google maps and I think it looked nice so I decided to give it a go. It didn't let me down. I ordered a prawn curry with rice and I liked it very much. Although it didn't taste like curry to me, the taste is very rich and fresh. It would just be perfect if it wasn't that expensive. (Everything's expensive there though)
Overall : ★★★★☆
By the way, make sure you wear strong and comfortable shoes before heading to Monaco. As you would walk a lot, by walk here, I mean, more like hike, to be specific.