Maria and Rosaria have been very lovely and helpful hosts! I stayed for four nights in the "grey" apartment. The place is very central - right next to the shopping area, the lively fish market and the park "Villa Bellini". It is also close to bus stations and only a 10-15 min walk to the central station or to the cathedral. Also two cinemas and many bars are closeby.
The small all-in-one-room apartment is newly furnished, cozy, clean, feels safe and has an open kitchen equipped with everything needed. At first I was a little staggered that there was no real daylight window (there is only a small window to an inner courtyard) - but it was ok, since therefore it was really quiet and I slept soundly. And rest and silence are hard to find in Sicily ;-)!!
Only one thing the hosts might need to look after: the wall in the gallery shows some signs of mildew.
I had a great time in Catania and thank my hosts very much!