Rooftop bars in Istanbul usually mean cocktails and a price to match. Tower Pub, on a roof in Sirkeci, is the plainer version: beer on tap, simple food, and a terrace with a view that costs nothing extra.
From the tables you can see the Galata Tower on the opposite shore, the ferries turning into the Golden Horn, and the skyline of the old city behind you. Come an hour before sunset and stay through it.
Open from midday until late, no reservation needed midweek. It fills up on Friday and Saturday evenings.
From Romance Istanbul Hotel it is a six-minute walk.