It’s not as spacious and fancy as it looks in the pictures. We were in six, and I think it was a bit small for us, I would recommend for maximum 4-5 person. It has only one toilet, but a tub and a shower also. The location is the best, the main square and the main attractions are very near, approx. 5-10 minutes walking (The Blue Mosque, Ayasofia, the Bosphorus, etc).
Yavuz and his uncle are very friendly, always write almost immediatly, they organized our transport back and forth too (it went clockwise), and recommended good restaurants, shops, supermarkets nearby.
All in all I would recommend their apartment in the city center! :) Thank you very much for everything!