Only a few hours' train ride from Dublin, Sligo is a beautiful beach town that while quaint, has a lot to offer. The beaches draw a young surf community that hangs out in the local pub near the water. The mountain hiking offers wonderful views, and you can take your pick of the charted or uncharted routes. It is close to castles, larger towns, and some historic sites including the W.B. Yeats Grave at Drumcliffe.
I traveled to Sligo to visit a close friend whose family lived there. Having the local tour guides certainly made finding all of the wonderful hidden treasures easy. We hiked for an hour on a path then started tromping through what looked like uncharted territory. I protested, but my friend assured me it would be worth it, and we stumbled upon this opening in the forest. We were enveloped by stunning walls of green. To this day my visit to "the glen" is my fondest memory of being close to nature.
If you have the opportunity to visit Sligo—ask around about the glen—I hope that it has not changed!