The mountain and the lake
Tonelagee means ‘backside to the wind’ in Irish – Tóin le Gaoith – and at 817 metres, the third-highest summit in the Wicklow Mountains, it earns the name. The reason most people climb it, though, is the view partway up: Lough Ouler, a glacial lake shaped almost exactly like a heart, held in a corrie under the northeast ridge. Its prominence of 202 metres makes it a Marilyn, and it also appears on the Arderin and Vandeleur-Lynam lists.
The lake is the whole point, so it is worth saying plainly: you see it from above. It sits at around 600 metres below a cliff face rising close to 200 metres, and the classic straight-down-on-the-heart shots you will have seen are usually drones. From the ground, the vantage is the ridge and the northeast top, and it is more than enough. The summit itself is a flat trig point.
The mountain lies within Wicklow Mountains National Park, a landscape of heather plateaux, glacial valleys and old stone monuments, and it sits on the central spine that runs from Kippure toward Lugnaquilla.
History and landscape
The name has turned up in old records in variant spellings such as Tonelegee. The rock underfoot is adamellite, a coarse granite studded with large microcline crystals, which gives the upper slopes their weathered, light-catching texture.
The shape of the place is glacial. During the last ice age, moving ice gouged out the deep amphitheatre that now holds Lough Ouler, and the cliff on its northeastern side frames the lake in a natural bowl. Locally the lake is also called Lough Iolar, ‘lake of the eagle’.
Walking routes
Tonelagee can be climbed from several sides, each a different balance of distance, gradient and scenery. None of the routes is signposted.
| Route | Approx distance | Time | Difficulty |
|---|---|---|---|
| Glenmacnass Loop (east) | ~8 km loop | 3.5–4.5 hrs | Challenging |
| Wicklow Gap (west) | ~4 km return | 2–3 hrs | Difficult |
| Turlough Hill (direct) | ~4.5 km return | 2–2.5 hrs | Moderate |
Glenmacnass loop (east)
The most popular and most photographed way up. From the Glenmacnass car park on the Old Military Road (R115), the path follows the Glenmacnass River and crosses on stepping stones, then climbs steadily through bog and heath. After a while you reach the Tonelagee NE Top (668 m), which gives the first clear look down into the corrie, Lough Ouler a dark heart against the slopes, and a natural place to stop. The route then follows the rim before the final steeper pull to the summit; on a clear day it opens a full circle over the Irish Sea and the surrounding ranges. The descent usually returns via Stoney Top (714 m).
Wicklow Gap (west)
From the Wicklow Gap car park on the R756, a well-trodden but unmarked track climbs the western shoulder to the summit ridge, with a short detour to the cliff edge over Lough Ouler. There are no technical sections, but the ground is soft and boggy after rain and the route is graded difficult for the sustained climb. A reliable option from the Glendalough side. The old Glendasan lead mines by the Wicklow Gap, worked for over 150 years, sit close to this trailhead.
Turlough Hill (direct)
The quickest ascent: a straightforward out-and-back of roughly 4.5 km from the Turlough Hill car park, steep at the start but clearly defined, reaching the summit area in around two hours with a short extension to the lake viewpoint. A good choice if you are short on time.
Extended ridge walks
Tonelagee links into a wider network of ridges. The Mullaghcleevaun–Tonelagee loop runs about 16 km over roughly six hours, connecting to Wicklow’s second-highest peak, and it has a reputation as one of the most energy-sapping and deceptive walks in the county: the ground keeps rising when you think it should not. Best left to experienced hill-walkers comfortable with open-terrain navigation.
Practical information
- Parking and transport: the Glenmacnass car park is the largest but fills fast at weekends. The Wicklow Gap and Turlough Hill car parks are smaller and free. Bus 183 (Arklow to Sallins) stops at the Wicklow Gap, about 1 km from that trailhead; check the Transport for Ireland timetable.
- Access and navigation: trails are not signposted, so carry a GPS device, offline mapping or a paper map. The Glenmacnass route includes a river crossing; check water levels first.
- Fees: entry is free, and the mountain is part of Wicklow Mountains National Park.
- Seasonality: open year-round. The Glenmacnass loop waterlogs after prolonged rain and its river crossing can be unsafe in high flow; the Wicklow Gap side stays firmer. Winter on the upper slopes calls for ice axe, crampons and navigation skills.
- Facilities: none on the mountain. The nearest are at the Glenmacnass Waterfall viewpoint and in the village of Laragh, about 10 km south.
- Safety and pets: loose boulders, steep ground and open bog; good footwear and layers matter. Dogs must be on a lead at all times in the National Park.
Nearby
- Glendalough – a monastic settlement in a glacial valley, about 8 km via the R756.
- Avoca Valley – river walks and craft heritage, reached via the R752.
- Blessington Lakes – angling and watersports, roughly 20 km away.
- Aghavannagh – a quiet village with access to the Glenmalure valley and forest walks.
Start early to beat the weekend crowds on the Glenmacnass route, allow time for the river crossing, and check the forecast: this is open, exposed ground and the weather turns quickly.