The main problem was dirt. The flat was quite dirty, it obviously hasn't been properly cleant. The ceilling in the bathroom was covered by some kind of black mildew. Despite the fact that it is an old building, it was possible to keep it clean and cosy, in an acceptable way to welcome guests, but it was not the case.
Pictures didn't match reality, so what appears to be a gleaming flat is actually a quite dark one, smelling of dampness.
We would have also appreciate have one towel per person, but there was only one.
Nevertheless, the host was very friendly and the appartment was well placed.