Glendalough is a hub for walking in the Wicklow Mountains National Park. The most popular routes start from the upper car park and range from the easy lakeshore circuit (about 3 kilometres, flat) to the demanding Spinc and Glenealo Valley loop (about 9 kilometres, with steep climbs and views over both lakes and the surrounding mountains). The Wicklow Way itself passes through the valley.
The Spinc Ridge walk is the highlight for those who want elevation: the path climbs through oak woodland and then breaks out onto open heath with panoramic views over the valley and the surrounding peaks. The boardwalk section along the Spinc ridge is well maintained and gives a good high-level perspective without technical difficulty. Allow 3 to 4 hours for the full loop from the upper car park.