I stayed 5 nights in Marco‘s apartment and enjoyed my holidays there a lot. You will find there everything you need. Also the big rooftop-terrace is amazing. From there you can observe the city and the vulcano Etna during day and night.
The apartment is very well located. Shops and many tasty restaurants are around the corner and the Fishmarket and the Piazza Duomo is only 10 minutes foot walk away. I highly recommend this apartment. I would book it always again for a stay in Catania.