This is such a good service and one I've been meaning to take advantage of for years.
The bus leaves Dawson street at 11:30, which was a good time for us, gave us enough time to have a little lie in, make a decent breakie to set us up for the day and then make our pack lunch.
We arrived roughly before 13:00, bought a walking map from the visitors centre and headed off on our 9KM walked around the lakes and the Glenealo Valley. If the distances on the map are correct and I would say that they are, from the drop off point of the bus, we did 12KM in all and boy do our legs feel it today.
Anyway I digress... so the bus then departs Glendalough at 17:30 to go back to Dublin, which gives you 4.5 hours to see the place. Which is more than enough to tootle around the monastery, the nearby lakes and waterfall. It's just enough time to do the Spinc and Glenealo Valley (White Route) at good pace.
I was taken aback by the price of the bus ticket though, 20EUR return from Dawson street. I think this is steep, even for Dublin. But I guess if you are the only direct bus service from Dublin to Glendalough, you can get away with it. I would probably use this service more often if it was cheaper. So I dropped a star for that.
My partner made the point that if you've got four/five people altogether who want to go to Glendalough, it would be just as easy and more flexible to hire a car for one day. I am inclined to agree with him.
* please check prices and timetables on their website in case any of what I've mentioned has changed! read more