We enjoyed our stay in Yildiz's apartment. It is 2 floors up from the street level, up a narrow staircase. The apartment itself is all on 1 level, which we enjoyed tremendously. Rooms are not huge, but that probably is to be expected staying in the Old Town Sultanahmet area.
Its best feature is its location. It is an easy 10-minutes or less walk to the main square where major attractions in the area like Hagia Sophia, Blue Mosque, Topkapi, and others are located.
The host was very nice and communicative ,and even brought us some very nice chocolates. The a/c worked very well.
Tip - Less than 10 minutes away (NW on Kadirga Street) is a simit bakery named Çolakoğlu Simit... fresh simit and other pastries every morning :)