I am really sorry about this issue and the situation you suffered while staying at my apartment. Before your stay, there had been an issue with the plumbing. It is a very old building and we found the problem in one of the bathrooms, underneath one of the showers. That was fixed, like I told you when you booked. However, during your stay, it appears that there was a plumbing problem again. I fully understand that this was not nice for you and your family. And I am really really sorry that this happened. I sent another plumber as soon as you left to check everything, I closed down the apartment for a few days, they broke open walls and found a sewage tube in one of the walls and there was a crack in the tube, causing the smell to come out. I have been going to the apartment whenever possible to see if I can detect any smell, and it has not smelled since the second intervention.
Again, my sincere apologies about this situation, and I hope everybody has good memories about the city.