The Poisoned Glen lies near Dunlewey in the Derryveagh Mountains of Donegal. Geological Survey Ireland describes the ice-shaped valley and its exposed granite, and the roofless old Dunlewey Church stands near the entrance to the glen below Errigal.
The name is often explained as a translator’s slip, the Irish neamh (heaven) read as nimhe (poison) by a 19th-century mapmaker, though it is only one of several stories. An older legend blames the one-eyed giant Balor of Tory, whose poisonous eye is said to have split the rock as it fell. Take your pick.
Walking into the glen
Confirm access and your route locally before walking into the glen. The valley floor can be wet, especially after rain, and the slopes are steep, so boots and waterproofs are sensible. Public access into the glen is not confirmed, so no route is described here. For a marked walk elsewhere in the range, check Glenveagh National Park’s trail guide.
The reward of the glen is its setting: an ice-carved granite amphitheatre in the Derryveagh Mountains, just outside the Gaeltacht village of Dunlewey, with Errigal rising over it. The ruined church at the entrance is worth the pause. It is roofless now, its pale stone standing out against the dark slopes behind it. Local lore adds a resident ghost, the green lady, if you are inclined to look for her.
Climbing on Bearnas Buttress
The glen has long been a climbing venue, with routes worked out here in the 1950s and 60s. The faces run north to north-west and get very little sun, so they need a long dry spell to come into condition. Climbers should confirm access and current conditions locally. If you are not climbing yourself, it is still worth looking up at the walls from a public viewpoint to take in the scale of the place.
Getting there and practical notes
- Viewing the glen: use an established public viewpoint, and park only where you can leave roads and gates clear.
- On the ground: no facilities should be assumed. Take everything back out with you, and keep dogs off livestock and nesting birds.
- Weather: mountain conditions turn quickly and the mobile signal can be patchy. Pack a shell and something to navigate with, and check Met Éireann before you set out.
Nearby
Errigal itself is right on the doorstep, the quartzite cone that dominates the view, and the glen lies toward Glenveagh National Park to the east. Down by the entrance, the Poison Glen viewpoint (spelled without the ‘ed’ on the signs) gives a look over Dunlewey Lough and Lough Nacung. The valley has crept into Irish music too: Clannad put a track called ‘Poison Glen’ on Anam in 1990, and Altan named a whole 2015 album Gleann Nimhe – The Poison Glen after it.