My friend and I went on the Giant's Causeway tour, and it did not disappoint. Our guide shared with us little bits of history about the place while interjecting them with folk legends, which definitely prevented things from being too dry. The sights were stunning too - the Dark Hedges (really cool especially if you're a Game of Thrones fan), Carrick-a-Rede bridge and Giant's Causeway were definitely a highlight. Belfast was a little underwhelming for me, but that might be due to the fact that we went on a Sunday, and most shops there were closed. Overall a must-do day trip if you're in Dublin!