Absolutely great apartment in the heart of Karaköy neighborhood, a few (steep) steps away from Istiklal Street, one of the main pedestrian shopping streets of Istanbul, as well as Galata Tower. The main tourist attractions in the center of Istanbul (Hagia Sophia, Blue Mosque, Grand Bazaar, etc.) are a very beautiful 45 minute walk away, less if you want to go by public transport, but really, why not walk? Dolmabahce Palace and the ferry to Kadiköy are also within walking distance.
The apartment is spotless, comfortable bed and a just-as-comfortable pull-out couch in the living room, nice balcony, and above all, the sauna is a great way to relax after a long day walking around Istanbul.
Furkan is also a great host, even though I didn't get to meet him in person he was very communicative and helpful at setting up a shuttle from and back to the airport.
Really recommend staying here!