Overview
Lough Ouler is the heart-shaped lake you may have seen on Instagram, but the heart only appears from above. Down at the shore it is just a mountain lake in a steep corrie. The corrie sits beneath Tonelagee, which stands 817 m in the Wicklow Mountains, and was scooped out by a glacier during the last Ice Age. There is no entry fee, but there is also no marked way to the lake: the ground around it is rough, boggy upland in Wicklow Mountains National Park.
A marked alternative
Leave rough, unmarked upland ground for experienced mountain walkers with navigation skills and suitable weather. This page does not describe a route to the lake. For a marked walk with lake views, choose one of the national park’s Glendalough trails, and combine it with the Glendalough monastic site. Check trail conditions before you set out.
Seasonal conditions and safety
Weather in the corrie changes quickly, and the ground underfoot decides how hard a day on the mountain is.
- Spring and summer are the more reliable seasons, with longer days and firmer ground after dry spells.
- Autumn brings golden slopes, but daylight shortens fast and rain is frequent.
- Winter brings snow and ice, and frozen bog turns treacherous. Only experienced mountaineers with cold-weather gear should consider any high ground in the Wicklows then.
Check the mountain forecast before any upland outing, tell someone your plans, and carry a map and a means of navigation. If mist drops visibility to a few metres, retreat to ground you can read. Cold, open mountain water offers no safety cover of any kind, and this page does not recommend swimming here.
What to see
The draw is the view from above, and it belongs to experienced hill walkers. From the high ground around Tonelagee the Wicklow valleys open out, with Mullaghcleevaun and Lugnaquilla framing the horizon on a clear day. The heart shape reads best from those high points rather than from the shore.
Wildlife keeps its distance. Red deer browse the heather at dawn and dusk, meadow pipits and curlews work the slopes, and birds of prey patrol overhead. The corrie is also reported to hold rare arctic-alpine plants, including mossy saxifrage and alpine lady’s-mantle.
Practical tips
- Gear: waterproof boots, warm layers, food and water. There are no facilities in the upland.
- Dogs: keep dogs on a lead in the park, and be aware that livestock may graze the lower slopes.
- Leave no trace: the bog is fragile. Stay on marked trails, take all waste home, and avoid trampling heather.