A lake in darkest Wicklow

Day 2 out east and we were taken on a tour around the Wicklow mountains stopping off at this very impressive lake. I can't remember where we were but the mountainside was steep and this little lad came hurtling down and the grass was slippy! 
We also had coffee at Powerscourt, visited a very beautiful cemetery for German prisoners of War, and marvelled at at grotto full of offerings where the BVM was said to have appeared.