Overview
Step off the N11 dual carriageway at Exit 9 and the noise of traffic quickly fades, replaced by the murmur of the Three Trouts River and the rustle of ancient leaves. The Glen of the Downs (Irish: Gleann na nDún, meaning “Valley of the Forts”) is a striking glacial valley on the east coast of County Wicklow. Its steep sides rise almost 250 metres, creating a natural amphitheatre that shelters a rare and thriving ecosystem.
Covering 100 hectares, this Special Area of Conservation is dominated by sessile-oak woodland on acid soils. It is one of the few places in Ireland where you can walk through a mature broadleaf forest featuring towering oaks, ash, cherry, and rowan, while keeping an eye out for red squirrels and the occasional pine marten. The valley is defined by a well-maintained 3.6km loop trail that climbs gently from the river floor to reveal sweeping views of the Great and Little Sugarloaf mountains.
The Walk & Trail
The reserve is best explored via the main circuit walk, which starts from the car park on the eastern side of the valley. The trail is clearly signposted and offers a moderate challenge with approximately 200 metres of ascent over the 3.6km route. Most visitors complete the loop in about an hour, though the path invites lingering at several lookout points.
The early section of the walk runs close to the N11, but the dense tree cover soon dampens the sound. As you climb, the path winds through a carpet of bilberry, wild garlic, and woodrush. The upper reaches of the trail open up to panoramic vistas across the Wicklow landscape. On a clear day, the Great Sugarloaf dominates the view, a fitting reward for the climb.
The ground can be soft and muddy after rain, so sturdy, waterproof footwear is essential. While the car park area is flat and accessible, the main trail involves inclines and uneven terrain that make it unsuitable for wheelchairs or pushchairs.
History & The Octagon
The valley’s Irish name hints at its deep past. The Glen of the Downs sits between two Bronze-Age hillforts, Coolagad and Downshill, dating to around 3,000 BC. Local legend suggests these forts were the stage for the Battle of Delgany in 1022, where Sitric Silkenbeard, King of Dublin, clashed with Uagaire, King of Leinster.
Centuries later, in the mid-18th century, the land became part of the Bellevue Estate. Dublin banker David La Touche purchased the 300-acre property in 1753 and built Bellevue House the following year. The estate’s most enduring feature is the stone Octagon, constructed in 1766. This eight-sided monument stands near the trail and is reputed to have been used for public executions, adding a sombre layer to its picturesque setting.
Bellevue House fell into ruin by the 1950s, and the Irish state eventually acquired the core of the estate. The Glen of the Downs was formally designated as a Nature Reserve in 1980, protecting the woodland for future generations.
Nature & Conservation
The Glen of the Downs is a stronghold for native wildlife. The mature oak canopy supports a rich understory of holly, honeysuckle, ivy, and wood sage. Botanists visit to spot rarer species such as Turner’s Threadwort (Trichocolea tomentella), a liverwort found at only five sites nationwide.
Animal sightings are common for those who walk quietly. Red squirrels are frequent visitors, often spotted darting through the upper branches. Sika deer, foxes, badgers, and otters also inhabit the reserve, while the elusive pine marten may be seen near the river. Birdwatchers can expect to hear blackbirds, chaffinches, jays, treecreepers, and wood warblers, with occasional sightings of red kites circling above.
Recent Expansion
The reserve continues to grow. In December 2025, the National Parks and Wildlife Service acquired an additional 40 hectares of adjoining land, increasing the reserve’s size by 68%. This new area, previously used for commercial conifer forestry, is being gradually converted back to native sessile-oak woodland. The expansion also allows for the removal of invasive species like cherry laurel and the conservation treatment of the historic Octagon, which is listed as a protected structure in the Wicklow County Development Plan.
Practical Information
- Getting There: The main car park is located on the eastern side of the valley, directly off the N11 at Exit 9 (Glenview). Parking is free but limited to roughly 30 vehicles, so arriving early on weekends is advisable.
- Public Transport: The nearest DART station is Greystones. From there, Bus Éireann route 84 runs to the reserve’s car park, a journey of about 10 minutes. Taxis are also available from the station.
- Facilities: There is an information board at the car park detailing the trail and local history. There are no café or toilet facilities on-site, so plan accordingly.
- Admission: Free entry.
- Duration: Allow 60–90 minutes for the full loop, depending on your pace and photo stops.
Nearby Attractions
If you have time to extend your visit, the charming village of Avoca Valley is just a short drive north. Here you can explore the historic Avoca Handweaving Mill, enjoy a pint in the village pub, or follow the peaceful riverside walk along the Avonmore.
Arrive early on busy days to secure a parking spot, and bring a waterproof jacket – the valley floor is often damp beneath the dense oak canopy, even on dry days.