Lovely hotel in a calm and cute area couple of blocks away from the bustling bazaars, but still entirely within walking distance. Kadiköy ferry is about 20 min away. In the immediate area surrounding the hotel, you'll find great breakfast options and some mini markets as well.
Room was clean and tidy, refreshed every day including the slippers, soaps and such, friendly and helpful staff, and indeed calm and quiet: The only noise we heard was birds in the morning. Our room view opened to the seaside which has no roads, instead a park with a walking path and beyond it, the sea. We stayed for three nights after a week in the Sultanahmet area, and it was such a bliss in comparison - should've just picked Riva's for the whole trip, really!
Among the boutique hotels in Istanbul, I believe Riva's Moda is top class, and I'll heartily recommend it!