Dyffryn Mymbyr from Pen y Gwryd Hotel

Difficulty: Hard

Distance: 19km

Time: 8Hrs+

Total ascent: 1350m

Technicality: Non technical mountain walking.

Terrain: Grassy mountain tracks. Very little constructed pathways

Navigation: Keen eye for following faint tracks. In poor visibility, good navigation skills with map and compass essential.


1 Start at the hotel. Cross the stile at SH 659 556. This first section is a bog fest. Wear your gaiters. Follow the old drovers track that leads across the open ground and in a SE direction, cross the stream at SH 667 551 and begin the climb. At about 669 549, keep left at the faint split and there will be a boundary fence about 50m to your left. If you lose the track, just handrail the fence all the way to Bwlch Rhiw’r Ychen. 

2. SH 676 542, cross the stile to the left and head East across the outcrop. Just as you come off the other side, at SH 579 543, there is an awkward, rocky step. Take care. Keep the fence close to your right hand side. Be aware of the steep ground on the other side of the fence. After the awkward step, it’s just a slog uphill, over Moel Gid and onto the summit of Moel Siabod. At SH 698 546, cross the fence and cross back left over the unnecessary stile at the foot of some rocky ground at SH 701 545. Skirt left around the worst of it and head roughly East to the summit.

3. SH 705 546 From the summit, avoid the awkward boulder field by keeping to the right, taking care for the steep slopes. Just before the ground rises in front, at about SH 707 548, cross to the left and pick up the track down toward Plas y Brenin. Near the start of the descent, keep to where the path is already eroded to not increase widening. As you get lower down, into more boggy ground, the track can be hard to follow, just head N/NE and you will pick it up again. Cross a few stiles, the last one being at SH 715 572.  Shortly after, you reach a split in the path. Take the left option, cross the forestry road and head down the track at SH 715 573. After around 100m at SH 716 575, turn left down hill, towards Plas y Brenin. 

4. SH 716 577. Cross the bridge, admire the view across Llynau Mymbyr, turn left at the road and then right, leaving the road at SH 714 578. This is private land, so stick to the access path to SH 719 584. From here, you break left (West) and follow the rough track uphill. There is no path, but the grass is well worn and followable up towards Cefn y Capel. Once you're on the broad ridge, the route finding should be straight forward. You're walking west to the crossing point at SH 692 582, where you'll keep right to the summit of Gallt yr Ogof. 

5. SH 685 585. From the summit of Gallt yr Ogof, bear SW to Y Foel Goch, then West to Llyn Caseg Ffraith. Classic Tryfan Photo location! 

6 SH 669 582. From the Llyn, the descent is S/SW. If in doubt, walk West 200m and then pick up the track South from there. The descent is straight forward. About 500m from the lake, at SH 668 578 the path steepens and bears SW, crossing a stream below a small waterfall. Just follow it all the way down, crossing the stile at SH 661 566 and handrailing the wall. As the ground becomes less steep, it gets wetter. If you've kept your feet dry this far, well done! You'll now be heading roughly S And in all but the worst visibility, the end will be in sight. Cross the river at SH 660 560 and head for the stile at SH 661 559 to finish. Enjoy the pint. 

GET THERE: Car is easiest. Otherwise train to Betws y Coed and taxi/bus is best. Sherpa available from Llanberis but inludes faff getting there from Bangor train station.

EAT & DRINK: Pen y Gwryd serve food if staying. If you don't have a room there, YHA Pen y Pass 5 min drive or Bryn Tyrch 10 mins. 

STAY OVER:  Pen y Gwryd! YHA Pen y Pass as back up/cheaper option. Llyn Gwynant if camping. 

BEST MAPS: (recommend up to 3, in this format please)

  • Harvey Super Walker XT 25 Snowdonia North. 

  • OS Maps OL17 Active map. 

Harvey/BMC Mountain map 1:40 Snowdonia North.