Mert's apt is really nice and lies in what we thought was the best neighbourhood in Istanbul: Kadikoy. Although Kadikoy is on the Asian side of the city, it's close to the harbour and a really nice ferry ride away form the European side that has most of the historical sites. Kadikoy has a great student, almost Berlin-like, vibe. Mert's house has everything you could need during your stay, and he's a flexible and welcoming host.