I recommend Mr Saban and his apartment. The apartment is big enough, sunny and clean. It is situated in a very good place, in the old city, close to the museums and historical objects. The surroundings seem to be safe and peaceful although they are very touristict (what influences the prices e.g. of food and restaurants). Mr Saban is very helpful and available at any time. We enjoyed our stay in Istambul also thanks to him.