Amazing apartment in an amazing location. I will definitely stay there again next time I'm in Istanbul. The apartment is modern, confortable, super clean, spacious and quiet. Balat is an amazing neighbourhood, full of awesome cafés and shops, and not a lot of tourists. Bits of the old Constantinople wall are nearby, including the gate that Mehmed the Conqueror used to enter the city in 1453.
Mehmet (the host, not the sultan) is a very friendly guy and gave us great tips on where to eat and wander around. It's also cheap to take a bus or a cab to other parts of the city, including the big touristy ones.