Kadıköy is a municipality and district on the Asian side of Istanbul Province, Turkey. Its area is 25 km², and its population is 467,919. It i…Kadıköy is a municipality and district on the Asian side of Istanbul Province, Turkey. Its area is 25 km², and its population is 467,919. It is a large and populous area in the Asian side of Istanbul, on the northern shore of the Sea of Marmara. It partially faces the historic city centre of Fatih on the European side of the Bosporus. It is bordered by the districts of Üsküdar, to the northwest, Ataşehir, to the northeast, and Maltepe, to the southeast.