Most visitors to Ireland start and end in Dublin, and most give it a single night before heading west. Give it at least two days.
Dublin
Dublin rewards time. The obvious attractions - Trinity College, Temple Bar, the Guinness Storehouse - are all worth seeing, but the city's real charm is in its neighbourhood pubs, its food scene, and the conversations you'll have with locals who are genuinely interested in where you're from and what you think of their city.
Getting Out of the City
Dublin sits on the doorstep of Ireland's Ancient East. Glendalough, the Boyne Valley and Kilkenny are all comfortable day trips, and each one shows you a version of Ireland the city can't.