We had a lovely stay at Mathilde's place. As with many Paris apartments, it is small, but it is perfect for a weekend. It's about 10-15 minutes walk to Sacre Coeur, and there are several good restaurants a short walk from the apartment. Super easy to get to from Gare du Nord. Worth noting there is no wi-fi at the apartment - this is listed, but we didn't check (not that it was a big deal).