Best City to Study Abroad in Ireland?

I am planning on studying abroad in Ireland the summer of 2011 and I cannot decide what city would fit me most. I was born and raised near Boston, MA and I go to school near Providence, RI, so I am hoping for a completely different city experience than those two cities; basically I don't want to feel like I could still be in America, I want to really feel like I'm living in Ireland (less modern, more old Irish buildings), if that makes any sense :) I am hoping for a city with a good nightlife and but one close enough to old castles, the countryside, and the ocean. My study abroad program allows me to choose between Dublin, Limerick, Cork, and Galway. If you could please let me know what city would be a good fit for me and why that would be great, thank you!!