Dyffryn Mymbyr has many opportunities for high quality bouldering – here’s some more for you to chew on. The main attraction is a large, pitched block with a steep front facet, which, remarkably, is clearly visible from the road. It provides some excellent problems with generally good landings. Si Panton was the plucky explorer who first got curious enough to make the 10 minute approach walk and check it out back in the winter of 2025. The rest is history…

Approach: park in the free layby 500m east of the Pen y Gwryd hotel. You can see the main boulder 200m to the south on the other side of the river. To reach it walk back towards the Pen y Gwryd for 170m, turn left and follow a vague path leading onto the embankment at the end of the reservoir. Follow the embankment round, along a short dam wall, and then to reach a small stream in front of the fence. Drop down left then cross the stream. Follow the barbwire fence left for 50m, to where it meets the main river. Cross the wooden fence section (important!), then walk up and leftwards to the boulders (100m). A more direct route can be taken but wet feet are more likely. NB. Please avoid climbing over the barbwire section of the fence, it’ll only end breaking the fence and/or your fancy kecks.

1. Cwrw Bach 6B
Up at the top of the eastern side there is an obvious line. Start sitting left hand on the spike/ledge under the bulge and right on a poor hold on the lip. Make a few snatches up then heave round to snag a good flake. Finish up leftwards. [Si Panton 02.25]

2. 6A
Start matched on the spike flake. Climb up right via break to lip and make a feisty mantel out onto the slab.

3. 7C
A desperate thin line left of the left arête. Start matched on the low undercuts, take a thin edge in the diagonal crease with your right and make a hard move up left to a small ripple above the lip of the overlap, then slap the top and mantel out directly. [Eadan Cunningham 22.05.25]

4. HD, HB Llaw Cwith 7B
A lefthand variation on HD, HB, but it feels very good and independent. Start right hand on the obvious finger flake on the steep left arete of the front face, left on a low undercut. Move up left with much difficulty to gain the lip. Mantel out directly, or scoot up left to a good hold before rocking out onto the upper slab. The lower Low Achiever start will add a bit of difficulty. [Pete Robins 02.04.25]

5. Hanner Dyn, Hanner Bisgedi 7A
The steep left arête of the front facet is brilliant. Start sitting, with a choice of positions on or below right of the obvious finger flake (as per Low Achiever). Move up rightwards via a confusing selection of poor holds to the lip, which is initially very slopey. Swing up right and exit onto the upper right hand slab by guppying the central fin. The direct mantel exit is a touch harder, but the same grade. [Si Panton 01.04.25, direct mantel finish: Pete Robins 02.04.25]

6. Low Achiever 7A
A low level traverse of the left side of the boulder. Start with hands matched on the low shelf just right of the left hand arête. Roll over to the starting finger jug on HD, HB, then use a low undercut to negotiate the low niche (just enough ground clearance with a skinny pad). Gain the flatty ledge out left and the large angular flake above. Continue leftwards with more difficulty, then a juggy section before a final couple of heaves to exit at the top left side of the boulder. [George Smith 04.25]

7. 7A
A standing start with a specified hand position: left dragging the finger jam sloper, and right holding an undercut down to the right. Make a hard pull for the slopey lip then swing up right and exit onto the upper right hand slab by guppying the central fin. A 7C sds eliminate has been done. Start with your left hand on a slopey sidepull on the arête and your right on the undercut. Move up and right, avoiding the finger jam sloper and using a poor sloper to its right (with your left), before jumping out right for the lip, etc. [Phil Targett 02.25, 7C eliminate: Luke Fletcher 22.05.25]

8. Pysgota am Obaith 7A
The equally steep right arête of the front facet is a beauty with a hard crux and an entertaining finish. Start sitting, right hand on the obvious pinchy hold on the arête, left pistol gripping the undercut fin. Gain the slopey lip with difficulty then swing leftwards and exit up on to the finishing slab by guppying the central fin. A lower hand position on the start can be forced, but there’s not much room and it’s awkward. [Si Panton 18.02.25]

8a. Pysgota am Ganmoliaeth 7A
As for the original, but at the top of the arête make slopey moves rightwards to a large flatty in the seam then mantel out left onto the slab. A less physical but more tenuous finish. [Si Panton 24.03.25]

8b. Pysgota am Sglodion 7A+
Start as per the original but move onto the right side of the arete, taking a diagonal undercut before snagging the top. Finish as per Pysgota am Ganmoliaeth on the right. [Pete Robins 02.04.25]

9. Hand of Wad 6B
Start sat on the shelf block right of the arête, left hand on a slopey flatty, right undercutting a block. Make a tricky reach to the large flatty in the seam on the lip and the same finish as per Pysgota am Ganmoliaeth. [Crispin Waddy 13.04.25]

10. Law o Duw 6C
Start as per Hand of Wad but then follow the slopey lip all the way up right to mantel round the right side of the final overhanging beak. [Si Panton 17.04.25]

11. Gulliver’s Traverse 7A
Start sitting as per Hand of Wad, but at the lip swerve left and follow the slopey lip line leftwards all the way round to finish at the top of Cwrw Bach. [George Smith 04.25]

There are some minor problems on the cluster of small blocks just above.

30m over to the right (facing up hill) an insignificant-looking jut of rock proves to be much bigger and better on close inspection.

12. Ditectif Gwnstbl 5C
The steep arête climbed from a sds. Superb! [Si Panton 05.02.25]

13. Marciau Brathu 6C
Start sitting on the right, rh on a good diagonal edge, left on a little rounded beak. Follow the diagonal seam out leftward into the arête. A slightly easier variant finishes as per Paid â bod yn Siarc. [Si Panton 05.02.25]

14. Paid â bod yn Siarc 6C+
The direct line up the leaning face. Start sitting, left in a thin horizontal slot, right on a little rounded beak. Hard moves lead straight up to a juggy exit. [Si Panton 17.03.25]

Easier slab lines on the two other adjacent boulders.

300m rightwards (if facing up hill), close to the diagonal path leading (eventually) to the Siabod ridge etc there are a few quality boulders.

The upper boulder has a steady line on the right, a blinkers line just to its left, but the main event is the line of flakes on the left side of the face:

15. High Altitude 6B+
A brilliant problem. Start sitting, rh: sidepull slot, left on a low undercut/pinch. Make a hard initial move to grasp a sidepull in a small groove on the left, then continue up to a good hold. Keep pulling, feet mostly smears to a friendly top out. 6A from a stand. [Stand: Martin Crook 1992, sds: Phil Targettt 2018]

The barrel shaped boulder to the right has a meaty traverse:

16. Cyfuniad Perffaith 7A
A sustained challenge, with no distinct crux, but likely to spit you off (perhaps) as you lose form on the final section? Start in a low crouch just right of the left arête, left in the crack, right in a diagonal slot. Move up for a few moves then head rightwards using a selection of holds, but staying below the upper lip. Finish past a good jug on the right. [Si Panton 21.03.25]

There are a few lines on the lower boulders here.

Over on the Glyderau side of the road there is more of the glorious dolerite to be found. To reach the best section follow the path opposite the free lay-by. This runs diagonally leftwards, crossing a new footbridge and passing an obvious (but disappointing) roof feature on the left. Continue up for a further 100m to a cluster of blocks. The large slabby block has a number of good problems up to 6A, but the main attraction sits just behind.

Sitting Bull 6C+
The hanging fin gives an absolutely class problem. Start sitting, left hand on the low pinch on the arête, right hand pistol gripping the lip. Make hard moves up to grasp the slopey shelf, then switch onto the left side of the arête, before rocking back round right at the top. [Crispin Waddy 2003]

Relevant links: