Cecilia's apartment is very nice and in a prime location for walking or taking the train to all of the parts of the city. The amenities were plentiful if you decide to stay in one night and the apartment is cozy. The entrance is on a small side street but the building and the apartment itself are very secure. I would definitely return and recommend the unit for a stay of any length in Paris.
The only thing to keep in mind is that it is on the third story with a very steep staircase in case there you have any mobility issues. Otherwise, you just get a nice workout carrying your luggage up the stairs to start your trip!