I was nineteen the first time I climbed Errigal. I remember the quartzite crunching under my boots and the realisation, about halfway up, that the mountain looks gentle from the car park and decidedly less gentle once you are on it. I also remember the drive in — the R251 narrowing through bogland, the peak suddenly filling the windscreen, the strange feeling that the mountain had been waiting for you to round that particular bend.
That is the thing about Mount Errigal. It announces itself long before you arrive. At 751 metres it is the highest summit in County Donegal, and because it stands alone on the Gweedore peninsula rather than hiding in a range, you can see it from an hour away on a clear day. The quartzite top catches the light differently from every angle — pink at sunset, steel-grey under cloud, almost white when the sun is high. For a lot of cousins on a Donegal road trip, Errigal is the photograph they end up framing on the wall back home.
This article is not a mountaineering guide. It is a driving-and-seeing guide. I will tell you how to reach Errigal by car, where to park, what the climb actually involves, and how to enjoy the mountain even if you have no intention of leaving the road. I will also talk about the Poisoned Glen, the valley that sits in Errigal's shadow and is, in my opinion, the most underrated part of the whole area.
Why Errigal Dominates the Donegal Skyline
Errigal is the highest of the Seven Sisters, a chain of steep quartzite ridges that runs across the north of Donegal. The mountain itself is not especially tall by international standards, but it is prominent. From the R251 between Gweedore and Dunlewey, it rises straight out of the bog with almost no foothills to soften the view. The result is a peak that looks bigger than it is, which partly explains why it dominates every "best of Donegal" list you will find online.
The quartzite is the other reason. Unlike the darker schists and granites you see elsewhere in the county, Errigal's upper slopes are pale and reflective. In low evening light the mountain seems to glow. If you are driving this part of Donegal on a day when the sun is doing anything interesting at all, you will pull over at least once to look at it.
What makes Errigal useful for a road trip is that it works as both a destination and a landmark. You can plan a full morning around the climb, or you can simply route your drive past it and treat the views as the attraction. Either way, it gives the northern half of Donegal a sense of place that the more famous southern coastline does not always provide.
The Drive to Mount Errigal: Approaches from Every Direction
The most direct approach to Errigal is from the R251, which runs between Gweedore and Dunlewey. If you are coming from the south or east, you will likely reach it via the N56 through Letterkenny and Churchill, then turn north on the R251 toward Dunlewey. From Glenveagh National Park it is about half an hour west on the R251 and R252. From the west Donegal coast around Glencolmcille or Ardara, you are looking at a longer drive — perhaps ninety minutes — but it is a useful connecting leg if you are doing a full Donegal loop.
The R251 itself is a typical Donegal secondary road. It is paved, but narrow in stretches, with grass growing up the centre in places and sheep that have decided the verge belongs to them. You will not need a four-wheel-drive, but you will need patience and a willingness to reverse into a passing place if you meet a local tractor or a campervan coming the other way. The speed limit signs are optimistic; the road conditions are the real limit.
Most visitors park at the trailhead car park near Loch Altan, on the eastern side of the mountain, or at the smaller pull-ins around Dunlewey on the western side. The Loch Altan car park is the one climbers use, and it fills up quickly on summer weekends and any day with good weather. If you are visiting in July or August, aim to arrive before 9:00 a.m. or after 5:00 p.m. to avoid parking on the verge, which is soft peat and has swallowed more than one rental car.
If you are not climbing, the Dunlewey side is more rewarding for a scenic stop. You get the mountain reflected in Dunlewey Lough, the old stone cottage at Ionad Cois Locha, and the Poisoned Glen stretching out behind. There is also a small hotel and café at Dunlewey if you need a coffee before the next leg.
Seeing Errigal Without Climbing It
Let me say this plainly, because the internet sometimes makes it sound as though a visit to Errigal is incomplete without the summit: most cousins will get more pleasure from looking at Errigal than from climbing it. The view from the road is extraordinary, and you do not need to be on the mountain to feel you have seen it properly.
The best roadside viewpoint is on the western side, along the minor road that loops past Dunlewey Lough. On a still morning the mountain reflects almost perfectly in the water. There is a lay-by near the boathouse that is wide enough for a few cars, and from there you can photograph Errigal with the lough in the foreground and the lower green slopes rising to the quartzite ridge. It is one of the easiest great photographs in Ireland.
Another good option is to drive the loop around the back of the mountain toward Loch Altan. The eastern face is craggier and more dramatic than the western face, and from the car park you can watch climbers picking their way up the scree. Even from the car park itself the scale of the mountain is impressive. Bring binoculars if you have them.
If you want a short walk rather than a climb, the path around Dunlewey Lough is level and takes about forty minutes. You get Errigal from several angles, and you also get a sense of how the mountain sits inside the wider landscape of bog, lough and glen. For many visitors, that is enough.
If You Do Climb: What to Expect on the Trail
The standard route up Errigal starts at the Loch Altan car park and follows a rough path northeast toward the ridge. The first section crosses wet bog, so waterproof boots are essential. After that the path steepens and the ground becomes loose quartzite scree, which is slippery on the way down and harder on the ankles than the ascent suggests.
A reasonably fit person will take an hour to an hour and a half to reach the summit. Most visitors take two hours up and an hour and a half down, with a total round trip of three to four hours including time on top. The final pull to the summit involves some easy scrambling, though nothing that requires ropes or climbing experience in dry conditions.
What does require respect is the weather. Donegal's mountains sit close to the Atlantic, and conditions can change within minutes. I have started up Errigal in sunshine and been in cloud and driving rain by the middle section. The quartzite becomes treacherous when wet, and the ridge is exposed. Check the forecast, start early, carry a waterproof layer and a spare warm layer, and turn back if the cloud drops below the ridge. The mountain will still be there tomorrow.
There are no facilities at the trailhead and no rescue service on call beyond the standard emergency number. Tell someone where you are going, or at least leave a note in the car. And do not underestimate the descent — more people twist an ankle coming down than going up.
The Poisoned Glen: The Valley Everyone Drives Past
The Poisoned Glen, Gleann Nimhe in Irish, sits on the northwest side of Errigal, between the mountain and the small village of Dunlewey. Its name comes from a local legend about poisoned berries or water, depending on which version you hear. Some historians argue the original name meant "heavenly glen" and was corrupted over time, which is the kind of thing that happens to placenames when English speakers try to write down Irish sounds.
Whatever the origin, the valley itself is the quietest part of the Errigal area. Most visitors head straight for the mountain and miss the glen entirely, which is a mistake. The floor of the Poisoned Glen is a mix of rough pasture and scattered oak woodland, with Errigal rising steeply on one side and the lower ridges of the Derryveagh Mountains on the other.
You can see the glen from the R251 as you drive toward Dunlewey. There is a small parking area near the church at the head of the valley, and a short lane that gives access to the valley floor. The land is partly private, so do not wander off the lane or through fields unless there is a clear public path and a stile. Treat it as a roadside viewpoint and a short, respectful walk rather than an expedition.
It photographs beautifully in the late afternoon, when the light comes in from the west and catches the upper face of the mountain while the valley stays in shadow. Give it twenty minutes and you will remember it longer than some of the more famous stops on your itinerary.
Photography and Timing
The classic Errigal shot is from Dunlewey Lough at sunset, with the mountain reflected in still water and the sky turning pink behind the ridge. You need a clear western horizon and no wind. Summer evenings are your best bet, though spring and autumn can surprise you.
Morning light works better on the eastern face. A start at first light gives you the best chance of clear summit views and decent photographs before the midday haze sets in. It also means you are back at the car before the afternoon clouds roll in.
Midday is the least interesting time photographically. The quartzite reflects the sun and the mountain can look washed out. A covering of broken cloud can rescue almost any hour, though. Some of the best Errigal photographs I have seen were taken when the summit kept appearing and disappearing through fast-moving Atlantic cloud. If the weather looks moody, wait ten minutes.
Where This Fits in a Donegal Road Trip
Errigal sits near the centre of north Donegal, which makes it a useful pivot point for several different routes. If you are basing yourself in Donegal Town or Letterkenny and want a day in the north, you can combine Glenveagh National Park in the morning with Errigal and the Poisoned Glen in the afternoon. That is a full day, but the driving between the two is reasonable and the landscapes complement each other well.
For a longer north Donegal loop, you could start at Glenveagh, head west to Errigal, then continue north to Dunfanaghy and Horn Head before looping back through Fanad Head. Those last two stops are spokes in this cluster that will be published soon, and the full northern section of the county deserves at least two days if you want to do it without rushing.
If you are coming from the south or west, Errigal works as a destination on the way to or from places like Slieve League, Glencolmcille and Ardara. I would not try to combine Errigal with Slieve League in a single day — both demand time and both involve driving roads that are slower than the map suggests. Better to give each its own morning or afternoon.
The broader route is covered in our main Donegal driving guide, which links every spoke in this cluster together. Whether you do Errigal as a half-day detour or the centrepiece of a northern loop, it earns its place on any Donegal road trip itinerary.
The Honest Verdict
Errigal is worth the detour even if you never leave the car. The drive in is memorable, the views from the road are as good as many summits elsewhere in Ireland, and the Poisoned Glen adds a layer of quiet atmosphere that balances the drama of the mountain.
If you do climb, go prepared. It is not a long mountain, but it is steep, exposed and unforgiving in bad weather. A good day on Errigal is one of the best experiences in Donegal. A bad day is a lesson in why Irish mountain rescue exists.
The mistake I see most often is trying to squeeze Errigal into an already packed itinerary. It looks close to everything else on the map, but the roads are narrow and the light deserves patience. Give it a morning, or give it an evening, and let the mountain do what it does best.
A Car That Gets You There
You will not reach Errigal by public transport in any practical way. The R251 is served by occasional local buses, but they do not run to a timetable that works for a sunrise climb or a sunset photograph. A car is the only way to give the mountain the time it deserves.
