I happened across this small exhibition centre a few years ago. It houses the National Archive of Irish photographs, which if you are interested can be viewed by appointment ( if you want to research a particular place or topic for example). However, it has an exhibition area in which a selected series of over-sized photos are displayed with a connecting theme, and accompanying explanations and wall text. It changes these exhibitions every few months. As it it near to Temple Bar, in Meeting House Square, it is easy to get to, and it's free of charge. It doesn't take too long to go round the exhibition, but it gives insight to the given topic, and so a little more background to "Irishness". Ideal if you only have a half hour or so, but want a bit more than just the usual tourist trap. You might be pleasantly surprised!