Our stay was a very unfortunate choice.
I have to recognise that the staff member that helped us with the check-in was very friendly and helpful (we chose late check-in with an extra cost as stated in the apartment's rules, due to the late arrival of our flight). Also, the location was very convenient, only a few minutes on foot to the main tourist attractions and the city center.
However, the apartment was not very clean, there was dust in the corners, the floor, but the major disappointment and the main source of our problem was the bathroom.
Even from the first hours of our stay, there was an intense smell, which seemed to be more intense in the bathroom. At first we thought that it was because of the sewage system (maybe an overall problem in the city?), but there was no cap to cover the toilet seat and the smells got out. Or maybe it was mold, since the small decorative plastic plants were covered with a thick grey layer. Later on we assumed that the unpleasant smell may have been coming from the aeration/ventilation on the bathroom ceiling, or at least the bad smell was distributed allover because of the aeration. We opened the window to air the flat and let the water run. However, the smell insisted. The next day we contacted the host, who gave us some advice (things we had already done) and told us that the problem may have been caused by the sewer system of the city and that they would check the issue the next day, when we would be gone (so it was meaningless for us).
At our last night, the smell was simply unbearable.
Also, we were unfortunate, since, when we arrived, we found out that the elevator had broken down and was under repair, so we had to go up and down 4 floors on foot plus we had to stand the noise of drills in the morning. The works for the elevator had not been completed until our check-out, so this was another inconvenience for us.
The apartment was also lacking shampoo, although it was listed as provided. There was only hand soap.
The only thing that somehow smoothed our disappointment was the convenient location and the fact that we were on sightseeing outside the house during the major part of the day.
Had we known the intense smell problem and the lack of elevator during our stay, we would have chosen otherwise.