Galataport runs along the Bosphorus between Karakoy and Tophane. The cruise terminal was built underground so the shoreline above it could stay open, giving about 1.5 km of public promenade where the docks used to be.
What is there: waterfront restaurants and cafes, a shopping level, and Istanbul Modern at the Tophane end. Entry to the promenade is free and it is open late. Facilities are good, the walkway is flat, and there is shade in parts of it.
From Hotel Yasmak Sultan the simplest route is the T1 tram to Tophane, about fifteen minutes. Walking is also possible via Eminonu and Galata Bridge if you want the crossing itself, which takes around twenty-five minutes.