This is a popular tourist spot in County Wicklow, not far from Glendalough. Unfortunately, I do not know the name of
this waterfall.  I do know that I have seen
this same shot of this same waterfall in many coffee table photography books on Ireland and if I do say so myself, my own shot rivals any I have seen so far.  This is one of the best photographs I've ever taken in my life and is the gem and "prize" of my personal collection.