Our stay was 27 - 29 July 2019, during the Festival. What a party! I didn't expect this, but the apartment sits upon one of the old-town streets through which the bands and processions pass, so all can be seen from the ample windows in the living room. The whole scene reminded us of the New Orleans Mardi Gras.
OK, especially for American sensibilities: when you first walk into the building's entry and stairwell, you will have thought you made a huge mistake. It looks like what you might imagine the worst sort of tenement housing in the U.S. might appear. I thought I just put my family into a situation for which my wife will never forgive me. Don't freak out. This is an ancient building in an ancient town, and just go with it; it's safe to proceed.
Once you enter the apartment, after one flight of stairs (no elevator), and gain access to the apartment by the keypad, you will breathe a sigh of relief. It is a wonderfully renovated, clean, airy apartment that has everything you need to be comfortable. The views of the street below are quaint and entertaining as a people-watching perch. If you don't understand the washer/dryer, do a youtube search.
The medieval town of Bayonne is a marvelous walking town. There is a supermarket within the town a short walk away, so cooking is an option, as the kitchen has everything you will need. We enjoyed our stay immensely, and would stay again.