This is a great apartment (even with the four flights of stairs)! It is in a great neighborhood with plenty of restaurants, coffee and pastry shops and shopping. It was lovely to be able to eat our late dinners just steps away from the apartment after long days of walking and having fun.
The apartment is a little over a mile from the Louvre and so it made walking there or to Musee d'Orsay the best way to get there (although Uber and taxis are plentiful).
The apartment has two shower/sink bathrooms and only one toilet (in a small closet-like room) and I was a bit worried with four of us, but it worked out fine. The kitchen is small but adequate since we didn't cook in it and it has a nice living room to hang out in.
One note - with the active neighborhood, this is not the spot if you need absolute silence to sleep! It did not bother us, even though we were often sleeping with the windows open, but there were some loud, drunk people who stayed out much later than we did.
The host, Joanna, is super-helpful and very responsive - a joy to work with!
Overall, we really enjoyed it - it is a very old building but the unit is charming and the neighborhood is awesome!