Vicar Street is consistently rated one of Ireland's best live music venues — a 1,000-capacity room on Thomas Street in the Liberties that manages to feel intimate even when full. The sightlines from the balcony are excellent, the acoustics are good, and the building has enough character (it occupies a former industrial space) to feel like a real Dublin venue rather than a generic box.
The programming ranges across folk, rock, comedy, and world music, with a bias toward acts that are too big for pubs but too small for arenas. It's worth checking the programme before you arrive in Dublin.