Karaköy is five minutes downhill from us and it is Galata's seaward side. A century ago it was the district of banks and shipping agents; today it holds coffee roasters, design shops and ironmongers who are still trading.
Coffee. Third-wave coffee spread through Istanbul from here. The lanes hold small stand-up places; the ones with tables are nearer the quay. Between nine and eleven is the best of it.
Fish. The fish restaurants beside the ferry terminal work at lunchtime. A plate of fish, meze and salad, by the water — busy, but real. For the evening, book.
The quay. The ferry terminal is here, for the Kadıköy and Üsküdar lines. The space in front of it fills up in the late afternoon; sitting and watching the Golden Horn costs nothing and is one of the best views in the city.
Art. There are small galleries and design studios in the district, some of them inside old hans. The doors are plain and the signs are small — do not be shy about looking in.
Shopping. Around Perşembe Pazarı, hardware and hand tools are still sold. It is not touristic but it is interesting to walk: this is Istanbul's working face.
About the hill. Down is five minutes, up is fifteen. For the way back in the evening, consider the Tünel funicular or a taxi — or simply do not plan to walk up from Karaköy at the end of the night.
A suggestion: go down in the afternoon, eat fish, meet the sunset at the quay, and finish the evening back up in Galata.