Not surprisingly, Glendalough has at least one reported ghost. We didn’t see anything there and I found the place to be wonderfully peaceful, but there is supposedly a hooded black figure – one of the monks, possibly St. Kevin himself?
The other ghost is supposedly a woman in red, who St. Kevin beat with nettles and then threw into the lake…oooooooookay. I’ve noticed a lot of ghostly legends revolve around supposedly moral/religious people doing hideous things.
A Grave Concern 
I went to that graveyard one night about 7 years ago with some friends, We planned on spending the night in the old monestry ruins and set u camp there, We lit some candles for a bit of light and sat down to talk, We were their for under 1 hour when we heard footsteps just outside the walls nearest the river, We got up and walked out the opposite opening and within 30 seconds about 6 men or ghosts dressed like monks walked out and stood side by side, I was scared sh”tless but i said hello, There was no reply from them whatsoever, Not a hello, Not a laugh,Nothing, Myself and my friends ran from that graveyard and to this day i don’t know weather it was a few guys having a laugh or something paranormal. I will never forget it do. Happened about 1 am summer of 04, 05.
Another Glendalough ghost of a monk here: http://www.boards.ie/vbulletin/showthread.php?t=2054896242&page=106