Kilmainham Jail is super. Great guided tour. Plenty of history. And not far to walk from the Suir Road stop on the Red Luas Tram line from the city centre.
I've done the Guinness tour twice. I was highly underwhelmed for the first tour. But a few years ago I revisited on St Patricks Day 2017 and the Incredible Guinness Tour on 17 March does not in any way shape nor form resemble anything like the standard tour on the other 364 days of the year.
Unless you are in town on St Patricks Day, I would say go to one of the older pubs in town for a pint of the black stuff - maybe O'Donoghues in Merrion Row or The Stags Head in Dame Court.
Also there is a small quirky museum on St Stephens Green near The Shelbourne Hotel - Its called The Little Museum of Dublin. Definitely book the guided Tour - and If you are there on the weekend, they also do a walking tour of St Stephens Green - It only happens once in the morning 11am, I think. They call it the Green Mile. The guides are fabulous. Pre-book as it sells out quickly.
