A visit to Dublin is not a visit to Dublin if one does not go to the Guinness Storehouse. Even if you do not drink, which is my case.
Guinness (pronounced /ˈɡɪnɪs/) is a popular Irish dry stout that originated in the brewery of Arthur Guinness (1725–1803) at St. Jame's Gate, Dublin. It is one of the most successful beer brands worldwide and very popular with Irish people both in Ireland and abroad and, in spite of a decline in consumption since 2001, it is still the best-selling alcoholic drink in Ireland, where Guinness & Co. makes almost €2 billion annually.
More info on that, visit: http://www.guinness-storehouse.com/en/Index.aspx