Staying at Nicolas place will allow you to walk to the Louvre in 10 minutes, Notre-Dame in 15, Saint Sulpice church in 7 and Delacroix Museum in 6. It is absolutely central and is in an area that is full of cafes, cinemas, restaurants and galleries. It will save you a lot of time and metro tickets by staying at Nicolas and of course Nicolas is such a kind and thoughtful host who makes you feel at home. Moreover, he gives so many tips about places to visit, shop and eat in Paris. I definitely recommend.