An ascent up Carnedd Llewelyn via Cwm Llugwy with a pathless descent that makes an ideal emergency descent if you need to cut your day short.
This walk starts at Glan Denau on the A5, past the Lake towards Capel Curig. You can either park here, or get the Sherpa here from Bethesda or Capel. If you use the Sherpa then you can catch the bus directly to the start of the Reservoir road, or alternatively camp at Gwern Gof Isaf and walk up from your tent.
Distance, Ascent and Time16.5km, 900m, 6.5 hours.
OS Map Required Explorer 017, BMC Map, Landranger 115
Difficulties Scrambling and steep scree, navigation.
Start/ End Glan Denau (on A5 near Ogwen)
Facilities None.
Public Transport Sherpa Buses from Bangor / Bethesda and Capel Curig.
The Route From Glan Denau, you need to take the stile on the same side of the road as Tryfan. This leads onto the original road through this valley built by one of the Lord Penrhyns and predates Telford’s A5. You have a nice easy walk now along this track as far as Gwern Gof Isaf, which is great to loosen the muscles. You also get views up of Tryfan and the climbers training on Tryfan Bach.
When you reach the second camp site, Gwen Gof Isaf, you can cut across to the main road, before carrying on for a hundred metres or so before you reach the start of the reservoir road. This is the start of the hard work. The track leads you, steeply at first before easing, as far as Ffynnon Llygwy reservoir where a break was well earned. Looking across the lake you can see the path ahead, first along the slopes of Pen yr 
Helgi Du before heading very steeply upwards to Bwlch Eryl Farchog. This section of path is rather steep and loose in places, so care is needed (its safer as an ascent than a descent).
You now feel that you’re up in the mountains proper, as you can see Llewelyn and the Carneddau, as well as the ridge up to Pen yr Helgi and the imminent climb up Craig yr Ysfa. This first section does involve a short section of serious scrambling. By that I mean you have to use all your limbs and pull yourself up and over to continue the path, but only for one section. Nothing too bad, but if you’ve not done a lot of scrambling it might pose a bit of a problem. The people in front of me took 3 attempts at a line, and by the time they got up were now the people behind me. I reckon they’d got an easier line though, along a sloping slab.
Beyond this, it’s all easy path to the top. You’ve done the majority of the climbing, so you’ll find yourself on top of the 1064m summit quite quickly. Today however, we decided to stop just before the final pull to the summit and shelter by some rocks for lunch. It was much cooler than it had been of late and we decided it might be a bit too nippy to stop on top. It was also busy, so we put out chances of getting shelter on top as slim.
Finally on top, there was no room to shelter, too busy. No problem as we were only staying on top for a short while. It was straight down, and it was decided to follow an untried route off the mountain. There is no path on the Craig Llugwy ‘ridge’ but i know 
it’s a feasible route. We turned off as soon as we could see the top of the broad ridge, towards what looked like a cairn. It turned out to be a rocky outcrop, but still a good pointer in the right direction. A very faint path leads down the ridge, and it’s all on easy grass if you can’t find it. From the ridge, you enjoy alternative views of the Carneddau and at one point you can see the lakes at Ogwen, Bochlwyd, Idwal and Ffynnon Llygwy. You also enjoy the silence, as we saw nobody on our descent (we saw one group ascend it in the morning), but many other people on other parts of the hill.
Make sure that as you reach the crags above the lake, Craig y Llyn, that you veer to your right as there is no safe way down through them (i know, i tried!). Instead, aim for the wall that should now be visible and parallel that to the road at the lake. If you find 
yourself on scrambling or very steep ground, then you’ve probably gone the wrong way. Make sure you’ve got your position right as the cliffs appear with little warning.
From the road, you just need to retrace your steps. Only this time, the reservoir road is much easier with gravity on your side.
