There are boats to and from Kınalıada, the nearest of the Princes’ Islands to the city centre, from Bostancı, Kabataş and Kadıköy. For times, search the Bostancı - Adalar Ring Hattı and Kabataş - Adalar routes on the Şehir Hatları (‘City Lines’) website. From the City Lines quay, walk in a southerly direction along the coast road, then turn inland along Ferit Tüzün Sokak, which will be the first street on your right after you have passed the Kınalıada Mosque. At the end of this street, turn left; Kınalıada Hristos Rum Ortodoks Manastırı (the ‘Kınalıada Christos Greek Orthodox Monastery’) will now be in front of you. The actual name of this institution is ‘the Monastery of the Transfiguration’. Wikipedia article