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Trail Running Guide to Lough Ouler and Tonelagee

Updated: Sep 27

Tonelagee lies deep in the heart of the Wicklow Mountains. The 817m mountain's name derives from the Irish Tóin le Gaoith which means backside to the wind. Both its peak and the Summit of Scarr form either side of the Glenmacnass waterfall, which at 80m in height it’s one of Wicklow's most spectacular! The ridge that its a part of forms the spine of the Wicklow Mountains going up to Kippure in the North and down to Lugnaquilla in the South. Not only is this mountain centrally located but it also has Lough Ouler nestled on its slopes. Wicklow's heart-shaped lake is a sight to behold. With this in mind it’s hard to think of a good reason why you shouldn’t check out Tonelagee and Lough Ouler!

To start off your run I’d recommend parking up at the Glenmacnass Waterfall car park. There’s a shorter trail from the Wicklow Gap but I personally prefer running the extra 2km so I can spend more time in the mountains. As we say with pretty much all our posts, we recommend you arrive early. There’s a big car park but the spots do fill up quickly on the weekends. Once you’re all laced up and ready to run, head to the edge of the forest by the river and start running North, away from the woods.

The trail at this segment of the run follows the Glenmacnass River. This river forms the Glenmacnass waterfall and continues on its course until it flows out into the Irish Sea as a tributary to the Avoca River. As you travel along the banks of the river be careful on the trail. It’s very narrow in parts and there are a few hidden rocks underneath the brush. During this time I would usually cross the river at some point. It’s really down to you to judge where to do this. I usually wait until I see enough large rocks in the water that I can cross on to avoid getting wet! You’ll have to keep heading North for about a mile before you turn West back facing Tonelage. A little trick I find that helps is I know once I’ve passed this stand-alone tree I know my left turn is coming up.

Where I cross the Glenmacnass River.
The lone tree

The first proper climb on this run is for about one mile and thankfully the trail is more obvious. That being said I find this part quite muddy so either bring really good footwear and gaiters or if you’re like me just be prepared to get wet! I found myself walking now and again on the way up and spent the time taking photos and catching my breath. Make sure you take a couple of photos to turn around and take in the view below. It can be quite an arduous climb but definitely not impossible so just be prepared to suffer a little bit.

Now you’ve made it to Lough Ouler, one of Wicklow's highest lakes as well as its only heart-shaped lake! I’d suggest everyone take a quick break at this point and soak up the view. One time when I was hiking this trail I decided to swim in the lake. I brought my trunks in my backpack as well as a towel. It was pretty refreshing, to say the least, and I found it incredibly enjoyable! If you do decide to swim in the lake, try set yourself up close to the bank and away from any obvious rocks in the water. It just makes it easier to walk in and out. After you’re done with your quick or not-so-quick break take the path to the right and follow it along the side of the lake. Once again the trail begins to narrow so make sure you watch your footing!

Follow the path with Lough Ouler to your left. This’ll lead you to your next climb. I’d highly recommend walking this part as it’s incredibly steep. With just over 1km to the summit, the average gradient is around 20%! Take your time and take in the views of Lough Ouler. As you gain altitude it’s much easier to make out the heart shape in the lake, so make sure you glance over your shoulder now and again. Be sure to keep an eye on the trail that you’re on as well. A lot of the time that I’ve done this route I usually enter the clouds around here. With the cliffs off to the left and a reduced level of visibility, it can very easily lead to someone being hurt if they’re not careful.

Lough Ouler

The trail will take you all the way to the summit so just keep on following it. Over the years people have laid out piles of rock to make the path easier to spot. Keep an eye out for them and for any curious sheep that live on the mountain. Then you’ll finally get to the top. From here you have two options to get back to the car park. You can either turn around and go back the way you came. Or you can head east on the trail. I prefer the second option as I get to run to Tonelagee‘s North-East Top, take in a different view and it’s slightly shorter than going back the same way you came.

Trail marker left by hikers
The Summit of Tonelagee

The descent is just under 4km but can be quite technical. Especially on the way down to the North East Top, and right at the very end to get back to the car park. Don’t try to rush down, especially on the rocky segments. If they’re in any way wet it can be very easy to slip on one. That being said this is my favourite part of the run. When you get past the rock scramble and are at the second peak it’s really fun to run. It’s not very technical, the trail opens up and the view looking down from your position is beautiful. The trail will narrow again at the very end. When you’re at this point you’re nearly there. Just descend as best you can down the slope, and cross the Glenmacnass River that’s the run complete!

If you’re looking for a technical run that’s not too long or too short this is a great option. Not only do you get the challenging climbs and trail, but you also get breathtaking views along the way. The run takes me around 1:30 usually so I like to incorporate it into a weekend morning, head home, and then have the rest of the day to do other things. If you’d rather hike it it’s still an excellent walk, just be sure to give swimming in Lough Ouler a go!

Click the photo above to be redirected to Lough Ouler and Tonelagee Loop on AllTrails

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