Croke Park, named after ArchBishop Croke the first patron of the Gaelic Athletic Association, is the finest stadium in Ireland and a place of pilgrimage for followers of gaelic games, by far the most popular sports in Ireland. The GAA is the largest sports organisation in Ireland and if you really want to get a sense of the heart of Ireland get yourself a ticket to a semi-final or final of the hurling or football competition. A wall of sound and naked tribal emotions (though in a completely safe environment) will be your award. 80,000 people can make a lot of noise (in the old days it was 120,000 but modern safety requirements have reduced the capacity and made finals tickets prized possessions!)
There is also a fine museum of the game which in a way illuminates the history of independent Ireland, as the GAA in former days was a major recruiting ground for those working for irish independence. In a famous incident during the war of independence, a match was interrupted in Croke Park when British forces surrounded the ground and opened fire on spectators and fans in reprisal for Irish attacks on crown forces (Bloody Sunday)
On the 15th of August, 2004 I went to the All-Ireland Semi-Final hurling match between Wexford and Cork. It was mad! I had watched a match on TV the week before, but it doesn't compare to being at a match! This game was held at Croke Park, Dublin and there was just over 62,000 people there. It was amazing, the game was great (although Wexford got crushed) and the atmosphere was fantastic - I loved it!!
I think for any sports fan, a trip to Croke Park whilst in Dublin is a must! Whether it is for a Hurling match or Gaelic football.
Or even when every second year there is International Rules, which is Ireland versus Australia in a hybrid game of Gaelic football and Aussie rules. It is taken in turns of being played in each country, there are two matches a week apart, points are on aggregate. Australia won the last test in Australia, 2005.