It is not a flat but a cheap apartment hotel hotel without services.
It is in walking distance to a lot of remarkable places (Grand Bazaar, Blue Mosque, Hagia Sophia, etc), however the surrounding is a bit rundown, and the hotel is not easy to find.
The apartment is nothing special, but eveything you need is there and working (air conditioning, fridge, hair dryer, etc).
Ercan, the manager is kind, effective, and helpful. Our communication was fast and accurate.