The Dark Horse on Hill Street in the Cathedral Quarter is one of the best bars in Belfast, a narrow Victorian pub with good whisky, craft beer, and a terrace that fills up on warm evenings. It's the kind of place that serves Guinness properly (cold glass, slow pour, rest, top-up) and has a selection of Irish and Scotch whiskies that would satisfy a serious drinker.
The bar attracts a mixed crowd of city professionals, tourists who've been pointed here by locals, and students. It's small enough to fill up quickly on weekends; go on a weekday evening for the best experience. The ground floor is standing-room-only; the upstairs room is calmer if you want to sit.