Overview
Glendun (Irish: Gleann Abhann Duinne – “glen of the brown river”) is the third of the nine celebrated Glens of Antrim in County Antrim, Northern Ireland. A narrow, glacier‑carved valley drops from the Antrim Plateau to the Atlantic, its floor dominated by the brown‑coloured River Dun, its hue derived from peat‑rich upland bogs. The glen is flanked by the seaside village of Cushendun, with its harbour and thatched cottages, and the hamlet of Knocknacarry. It lies within the Antrim Coast and Glens Area of Outstanding Natural Beauty, a patchwork of steep slopes, open moorland, ancient woodlands and stone‑wall‑lined pastures.
History & Legends
The landscape dates to the last Ice Age, when massive glaciers gouged deep U‑shaped valleys into the basalt plateau. As the ice retreated, the River Dun cut its sinuous channel through the newly exposed rock, creating the dramatic gorge seen today. Human settlement stretches back centuries, with descendants of native Irish families and Hebridean Scots who arrived during the Plantation era.
The Glendun Viaduct – Engineering Heritage
Between 1834 and 1839 the three‑arch stone and iron Glendun Viaduct – locally called the Big Bridge – was erected as part of the ambitious coastal road linking Ballycastle with Ballymena. Civil engineer William Bald designed the structure, while Sir Charles Lanyon acted as surveyor. Master builder Mr Bowells of County Monaghan, assisted by craftsmen from County Donegal, sourced stone from the cliff at Layde, shipped it to Cushendun and carted it up the glen.
The viaduct was officially opened on 16 May 1893, after a series of final works and road improvements. It quickly became a landmark of the Grand Military Way, later the Antrim Coast Road and now the Causeway Coastal Route. Preservation of the bridge has been supported by heritage‑fund grants and community arts initiatives, ensuring the stone arches remain in good condition for both traffic and visitors.
The glen also features a darker chapter of local lore. In the late 16th century, Sorley Boy McDonnell used the secluded valley to launch a night‑time ambush on an English cavalry force at the Battle of Orra. The English troops became mired in a peat‑filled swamp and were defeated; among the dead were Rory McQuillan, Hugh O’Neill and Capt. Thomas Catterton. Near the lower woods of Craigagh Wood a small penal‑worship site can still be seen, hinting at the covert religious practices of the 17th century.
Scenic Drive
The glen is traversed by the single‑lane B14, part of the famed Causeway Coastal Route. The Glendun / Glenaan Scenic Route covers about 18 miles (29 km) and saves roughly 4 miles compared with staying on the main coastal road through Glencorp. The drive offers continuous views of forest, river and stone walls, but the road is narrow, frequently shared with farm machinery, sheep and local traffic – not suitable for RVs or minibuses. Pull‑in mirrors at the lay‑by at Barnish and at the viaduct are essential for safe passing.
Heritage & Preservation of the Viaduct
- Built 1834‑1839, opened 1893
- Three stone arches with iron ribs, spanning the River Dun
- Known locally as the Big Bridge
- Listed as a historic engineering structure; recent preservation work funded by the Heritage Fund and community foundations
- Occasionally closed for maintenance – check local signage before travelling
Geology & Minerals
Glendun lies on the Antrim Outlier of Upper Dalraidian rocks, dominated by quartz‑mica schists. The River Dun cuts through these formations, exposing excellent outcrops that attract geology enthusiasts. Mindat records the presence of tourmaline and quartz specimens in the valley, making it a modest field site for amateur mineral hunters (always seek landowner permission).
Nature & Wildlife
The peat‑stained River Dun supports a healthy run of salmon and sea trout, making gentle angling a popular activity (catch‑and‑release is encouraged). Birdwatchers can spot dippers, treecreepers, jays and occasional golden plovers along the riverbanks. In spring the forest floor is carpeted with bluebells and wild garlic, while autumn brings a splash of amber and crimson across the oak‑pine canopy.
Fishing & Angling
- Salmon & sea trout – best run from May to September; local anglers recommend casting near the lower falls.
- Permits – no entry fee, but a rod licence from the NI Fisheries is required.
- Catch‑and‑release – strongly advised to protect the spawning runs.
Walking & Hiking
Marked trails range from short 2‑km loops to longer 8‑10 km hikes that climb from the coast up to the tundra‑like slopes of Slieveanorra. Popular routes include:
- Glendun Viaduct Loop – a 2 km walk that crosses the viaduct and offers panoramic views of the river and forest.
- River Dun Riverside Walk – a gentle 3 km path suitable for families, following the river’s meanders and passing several small waterfalls.
- Upper Glen Trail – a 7 km moderate hike that climbs into the moorland, providing vistas over the Atlantic and the surrounding glens. Navigation can be challenging; carry a 1:50 000 OS map (Sheets 5 & 9) or download an offline GPS track as mobile signal is patchy.
Wildlife & Birdwatching
Beyond the river species, the glen’s mixed oak‑pine woodland hosts golden plovers, redstarts, and buzzards on migration. Early mornings are ideal for spotting dippers darting over the water.
Dog‑Friendly Advice
Dogs are welcome on all public trails. Keep them on a lead near livestock and be mindful of the narrow single‑lane sections of the B14 where traffic can appear suddenly.
Practical Information
- Location: County Antrim, Northern Ireland; GPS approx. 55.12° N, 6.04° W.
- Access: B14 (Causeway Coastal Route). Parking is available at the Cushendun village car park, at the lay‑by near the viaduct, and at the Barnish lay‑by between Cushendall and Cushendun.
- Opening Hours: The viaduct and surrounding public land are open year‑round; no entry fee.
- Facilities: Restrooms and a visitor information kiosk are located in Cushendun. Local cafés serve tea, coffee and traditional Irish fare.
- Safety: The viaduct road is single‑lane and may be narrow; exercise caution when vehicles approach. River banks can be slippery after rain.
- Best Time to Visit: Late spring to early autumn offers reliable weather and vibrant foliage; early morning light is ideal for photography of the viaduct.
Glendun combines natural beauty, rich cultural history and engineering brilliance, making it a rewarding stop on any tour of the Antrim Coast.