Nicolas' apartment is a cozy and very comfortable retreat from which to explore Paris. Personally I really loved the typical 'French balcony' which the apartment has.
Located in the Montmarte district, it is only a Métro ride away from most sights and landmarks in Paris. You won't have to travel more than 20-30 minutes to get to pretty much anywhere in Paris. The most important Métro stations in the area are Abbasses and Pigale, both located at a short walk from the apartment.
Also, Montmartre feels a lot like a village: not as busy or hectic as central Paris, the district has a unique 'village-like' atmosphere to it. It is a very peaceful place to stay whilst you're in Paris. I absolutely recommend it.