I want to say, I don't want people not to stay here because of the following information. I think for someone without allergies, especially for a few days, would be happy here. I had to cancel and move to a new place because I was going to be staying a month, and would have been sick with allergies.
However, the whole house is damp and smells of mildew. I think this will be true of any basement apartment. It is only 2 feet below ground, but it is enough in Rome for it to be damp. There is a dehumidifier but it doesn't protect against mold unless it runs daily without a break of more than 48 hours (the time it takes for mold to grow). Also, it has many bugs - another symptom of it being below ground level, especially little flies in the bathroom. If mold and damp don't bother you (they really don't bother everyone!) it is a nice enough place.
The plus side of the damp is that it is very cool and has good air conditioning as well. It is hard to find a cool place in Rome at the height of summer, and this definitely is.
It is a good price for so much space- room for 3-4 to sleep, but note that the second bedroom is only divided from the first by a thin folding door and one has to go through the main bedroom to get to it. It would be ideal for families for that reason.