The GPO is famous for being the centre of the 1917 Uprising. When I went to Dublin before I did go and use it and the main hall has lots of pictures relating to its piviotal part in the history of modern Ireland.
About 10 years ago I made a documentary about my Great Aunt Mary (Fraser Dott). She was a founding member of the Scottish Nationalist Party and to my astonishment discovered that she along with other members of the SNP had gone to Ireland before WW2 and had a secret meeting with Irish Free State leader Eamon de Valera.
Article about the central mythologising role of the GPO in Ireland.