Take a moment to really learn the culture of Ireland and visit Croke Park. The people of Ireland are Gaelic Football and Hurling fanatics. It's only proper to find out for yourself what it is all about and the locals will be impressed when you hit up the nearby pubs. This stadium has seen many historical events take place, including Bloody Sunday in 1920.
It is a place that has yet to become uncovered by foreign travelers unless they follow the sport. Better yet, plan to go on a game day and experience it for yourself.