Overview
Glendun is the deepest of the nine Glens of Antrim, and the brownest: the River Dun that carved it runs the colour of strong tea, stained by the peat bogs on the upper slopes of Slieveanorra. Its Irish name, Gleann Abhann Duinne, means exactly that – “glen of the brown river”. A steep-sided U-shaped valley gouged by Ice Age glaciers, it drops to the Atlantic between the seaside village of Cushendun and the quiet hamlet of Knocknacarry, entirely within the Antrim Coast and Glens Area of Outstanding Natural Beauty. It’s the quiet one, too: the southern glens get the coach traffic, Glendun gets the single-lane road and the solitude.
The Glendun Viaduct
The glen’s most striking feature is the three-arch stone Glendun Viaduct, affectionately known locally as the Big Bridge. Constructed between 1834 and 1839, it was a vital component of the broader coastal road project designed to connect Ballycastle with Ballymena. Civil engineer William Bald designed the structure, with Sir Charles Lanyon acting as surveyor. Master builder Mr Bowells of County Monaghan, assisted by craftsmen from County Donegal, quarried stone from the cliffs at Layde, shipped it to Cushendun, and carted it up the valley.
Following its completion, the viaduct was integrated into the local road network, carrying traffic across the River Dun. Preservation efforts, supported by heritage grants and community initiatives, have kept the stone arches in excellent condition. The bridge is best viewed from the glen road, where you can slow down and take in the scale of the structure against the valley walls.
Walking & Exploring the Glen
Unlike the more heavily trafficked southern glens, Glendun offers a sense of wildness and quiet. There are no formal waymarked trails, but the narrow single-lane glen road provides easy access for walkers who prefer to wander on foot. Popular routes follow the River Dun upstream, winding through mixed oak and pine woodland where the forest floor carpets with bluebells and wild garlic in spring.
For longer hikes, tracks climb from the valley floor toward the upper moorland of Slieveanorra, covering roughly 8 to 10 kilometres return. The terrain becomes rugged and exposed at higher elevations, offering sweeping views over the Atlantic and neighbouring valleys. Navigation requires care: mobile signal is patchy in the valley bottom, so visitors should carry 1:50,000 OS maps (Sheets 5 & 9) or download offline GPS tracks before setting out. Early mornings are ideal for photography, when the mist often clings to the river and the viaduct catches the low light.
History & Local Lore
The glen’s history stretches back centuries, shaped by native Irish families and Hebridean Scots settlers. It also played a role in a pivotal 16th-century conflict. In the late 1500s, Sorley Boy McDonnell used the glen’s secluded, peat-filled terrain to launch a night-time ambush on an English cavalry force at the Battle of Orra. The English troops became mired in the swampy ground and were defeated, with several commanders killed.
A quieter, more somber chapter of local history can be found near the lower woods of Craigagh Wood, where a small penal-worship site remains. Dating to the 17th century, it hints at the covert religious practices of Catholics during a time when open worship was restricted. Today, the glen’s stone walls, ruined cottages, and quiet lanes reflect generations of agricultural life that have shaped the landscape.
Wildlife & Nature
The peat-stained River Dun supports healthy populations of salmon and sea trout, making it a favourite spot for gentle angling. Catch-and-release is strongly encouraged to protect spawning runs. Birdwatchers will find the valley’s mixed woodland and riverbanks rich with species including dippers, treecreepers, jays, redstarts, and occasional golden plovers. In autumn, the canopy shifts to amber and crimson, while winter brings a moody, atmospheric quality to the upper slopes.
Practical Information
- Access & Driving: The glen is traversed by the local Glendun Road, which forms part of the Glendun / Glenaan Scenic Route. This 18-mile loop saves roughly 4 miles compared with staying on the main coastal road through Glencorp. The road through Glendun is single-lane, narrow, and shared with farm machinery and livestock. It is not suitable for RVs, minibuses, or large coaches. Pull-in mirrors at the Barnish lay-by and near the viaduct are essential for safe passing.
- Parking: Free parking is available at the Cushendun village car park, the lay-by near the viaduct, and the Barnish lay-by between Cushendall and Cushendun.
- Facilities: Public toilets and visitor information are located in Cushendun. Local cafés and pubs serve tea, coffee, and traditional meals.
- Dogs: Well-behaved dogs are welcome on all paths and trails. Keep them on a lead near livestock and be cautious on narrow road sections where traffic can appear suddenly.
- Best Time to Visit: Late spring through early autumn offers the most reliable weather and foliage. Winter visits are possible but require sturdy footwear and weather-appropriate clothing due to icy patches and shorter daylight hours.