The Glendalough Valley is all about walking. There are nine waymarked trails in the valley, the longest of which is about 10km, or about four hours' walking. Before you set off, drop by the National Park Information Office and pick up the relevant leaflet and trail map. It also has a number of excellent guides for sale – you won't go far wrong with Joss Lynam's Easy Walks Near Dublin or Helen Fairbairn's Dublin & Wicklow: A Walking Guide.
A word of warning: don't be fooled by the relative gentleness of the surrounding countryside or the fact that the Wicklow Mountains are really no taller than big hills. The weather can be merciless here, so be sure to take the usual precautions, have the right equipment and tell someone where you're going and when you should be back. For Mountain Rescue call 112 or 999.
The easiest and most popular walk is the gentle hike along the northern shore of the Upper Lake to the old lead and zinc mine workings, which date from 1800. The better route is along the lake shore rather than on the road (which runs 30m in from the shore), a distance of about 2.5km one way from the Glendalough Visitor Centre. Continue up to the head of the valley if you wish.
Alternatively you can walk up the Spink (from the Irish for 'pointed hill'; 380m), the steep ridge with vertical cliffs running along the southern flanks of the Upper Lake. You can go part of the way and turn back, or complete a circuit of the Upper Lake by following the top of the cliff, eventually coming down by the mine workings and going back along the northern shore. This circuit is about 6km long and takes around three hours.
The third option is a hike up Camaderry Mountain (700m), hidden behind the hills that flank the northern side of the valley. The path (not waymarked) begins opposite the entrance to the Upper Lake car park (near a 'Wicklow Mountains National Park' sign). Head straight up the steep hill to the north and you come out on open mountains with sweeping views in all directions. You can then continue west up the ridge to Camaderry summit. To the top of Camaderry and back is about 7.5km and takes around four hours.
The Wicklow Way – Glendalough to Aughrim
The 127km Wicklow Way (www.wicklowway.com) is one of Ireland's most popular long-distance walks because of its remarkable scenery and its relatively fluid and accessible starting and finishing points – there are plenty of half- and full-day options along the way.
This section is 37km long and takes you through some of the more remote parts of the Wicklow Mountains and down into the southeastern foothills. There's relatively little road walking; the greater part of the day is through conifer plantations. The walk should take between 7½ and eight hours, with an ascent of 1035m.
From the National Park Information Office on the southern side of Glendalough's Upper Lake, climb the yellow-waymarked trail beside Lugduff Brook and Poulanass Waterfall. Veer left when you meet a forest track, then left again at a junction and cross two bridges. The Way leads northeast for about 600m then, from a tight right bend, heads almost directly southwards (via a series of clearly marked junctions), up through the conifer plantations, across Lugduff Brook again and beside a tributary, to open ground on the saddle between Mullacor (657m) and Lugduff (652m; 1¾ hours from Glendalough). From here on a good day, massive Lugnaquilla sprawls across the view to the southwest; in the opposite direction is Camaderry's long ridge above Glendalough, framed against the bulk of Tonelagee. Follow the raised boardwalk down, contour above a plantation and drop into it where a steep muddy and rocky path descends to a forest road; turn left.
If you're planning to stay at Glenmalure Hostel, rather than go all the way down to the crossroads in Glenmalure, follow the Way from the left turn for about 1km southwards. At an oblique junction where the Way turns southeast, bear left in a westerly direction and descend steeply to the road in Glenmalure. The hostel is about 2km northwest.
To continue straight on along the Way from the left turn, follow forest roads south then southeast for 1.6km to a wide zigzag above open ground, then contour the steep slope, swing northeast and drop down to a minor road beside two bridges. Continue down to an intersection and Glenmalure; it's about 1¼ hours from the saddle.
The Way presses straight on (south) through the crossroads for 500m, across the River Avonbeg and past silent Drumgoff Barracks, built in 1803 but long since derelict, then right along a forest track. Keep left past a ruined cottage and start to gain height in two fairly long reaches; go through two left turns then it's down and across a stream. About 800m further on, turn right along a path to start the long ascent almost to the top of Slieve Maan (550m) via four track junctions, maintaining a southwesterly to south-southwesterly direction. Back on a forest track, the Way turns left (southeast) close to unforested ground to the west. With a few more convoluted turns, you're out of the trees and on a path between the plantation and the road (mapped as the Military Rd). The Way eventually meets the latter beside a small tributary of the River Aghavannagh (two hours from Glenmalure).
Walk down the road for about 250m, then turn off left along a forest track, shortly bearing left to gain height steadily on a wide path over Carrickashane Mountain (508m). Descend steeply to a wide forest road and continue down for about 1km. Bear right to reach a minor road and turn right. Leave the road 500m further on and drop down to another road – Iron Bridge is just to the right (an hour from Military Rd).
Walk 150m up to a road and turn left; follow this road down the valley of the River Ow for 7.5km to a junction – Aughrim is to the left, another 500m. Buses on the Dublin–Wexford route stop here.