Sinister Gully: Route Description, Video & More

By The Bald Scrambler

Sinister Gully

Published By: Daniel Woodley. Updated: 20th March 2024. Filed at: Glyderau Scrambles. Disclosure: I may earn a commission from purchases made via links. Disclaimer: Scrambling and climbing are dangerous sports, this route description does not provide step-by-step instructions. Read Disclaimer.

Sinister Gully is one of the most popular routes in Snowdonia and combined with Bristly Ridge, is one of the classic scrambling lines in the UK.

I’ve already published a guide and video for those who wish to scramble up the neighbouring Dexter Gully but Sinister is the route most people will take but how difficult is it? What can you expect?

Keep reading to find out.

A Warning:

This is a grade 1 summer scramble but is considerably more dangerous in winter conditions where rope, axes, crampons and winter skills are often required.

I hope enjoy this page but I do not provide complete step-by-step instructions and neither do I highlight every danger.

If you are unsure of your ability to complete this summer scramble/winter climb, there are plenty of mountain guides who can take you out for a fun, safe day in the mountains.

Approach – How to Get to Bristly Ridge and Sinister Gully

My parking map displays over 250 spaces, many of them in laybys and free car parks.

I almost always scramble up Tryfan’s North Ridge first and then descend via the south ridge to the col (Bwlch Tryfan on maps) before going up one of the gullies and onto Bristly Ridge – this longer route makes more a day of it and the Tryfan/Bristly Ridge combo is a popular pairing.

If you’d prefer a more direct route, try one of these:

Bristly Ridge Approach

Imagery © 2023 Google, Airbus, Bluesky, Infoterra, COWI, Cnes/Airbus, Getmapping PLC, Landset, Maxar Technologies

From Ogwen Cottage

Take the path left of the toilet block near Ogwen Cottage up the wide steps and after a short distance, take the left fork and follow over a footbridge. After 200 metres or so, the path will curve rightwards, take a slightly narrower path to the left, ascend a steep path next to and then over a stream up to the left bank of Llyn Bochlwyd.

Continue to the pass where you’ll see a stone wall in front of you, Tryfan’s south ridge to your left and Bristly Ridge to your right.

From Gwern Gof Uchaf Campsite

Park in the long layby below Tryfan and take the path between the A5 and Tryfan up to the rear of the campsite, go over the steps and take a right, following the obvious path to the left of Little Tryfan (Tryfan Bach) – a popular climbing area.

As the path rises, go over the steps at the top and follow the path to Bwlch Tryfan – a col at the foot of Tryfan’s south ridge, which marks the start of the route up Sinister Gully and Bristly Ridge.

Find The Man-Made Retaining Wall

A short man-made retaining wall separates Sinister Gully from Dexter Gully. You’ll need to go over the wall to enter Sinister Gully (see photo).

Dexter Gully and Sinister Gully

Sinister and Dexter Gullies and the stone wall.

Map - How to Get to Sinister Gully & Bristly Ridge

Imagery © 2023 Google, Airbus, Bluesky, Infoterra, COWI, Cnes/Airbus, Getmapping PLC, Landset, Maxar Technologies

Retaining wall below Sinister Gully and Bristly Ridge

The retaining wall directly beneath Sinister Gully.

How to Scramble Sinister Gully

Sinister Gully is far more stable than the neighbouring Dexter Gully, and it’s mostly solid rocks and good holds all the way up to the top.

The start is a series of steps to scramble up; the going here is fun but never goes beyond a summer grade 1 if you stay in the gully bed.

The start of Sinister Gully

Alan scrambling up the start of Sinister Gully.

Looking down Sinister Gully

Looking down at the mid-section of Sinister Gully.

The Crux of the route is a steep section that I’ve heard being called “the wall” on several occasions.

It’s not a wall at all, just two large rocks jammed next to each other with a very narrow gap between them:

The crux of Sinister Gully

The crux of the entire route.

The best way to get over this section is to go straight up the middle, making use of the solid footholds available.

The clamber over the top will likely be less than gracious and it’s somewhat more difficult in the wet, although this is a popular route and the rocks are mostly clean.

The Avoidance Line

The steep section can be easily bypassed by taking a line out to the left. The scrambling here is easier and after a few metres, you can rejoin the main gully, above the tricky wall.

Sinister Gully Avoidance Line

Alan taking the left avoidance line.

Topping Out of Sinister Gully

The top section of Sinister Gully widens and is shallower but still fun to ascend.

From here, the views of Tryfan look impressive.

The top of Sinister Gully

The top section is broader and slightly shallower

Descents and Continuation

I don’t recommend descending Sinister Gully as the steep section could be problematic, although, for an experienced scrambler, the avoidance line is doable in reverse.

I certainly don’t recommend descending via Dexter Gully next door as that route is full of loose stones and mud.

Most scramblers continue up onto Bristly Ridge proper and then onto Glyder Fach. Sinister Gully isn’t usually scrambled without a continuation and from Glyder Fach, there are dozens of routes one can take.

Comparing Sinister Gully to Dexter Gully – Which Should You Choose?

If you’ve never scrambled up Bristly Ridge before, I suggest going up Sinister Gully, the handholds are more solid, and there’s less sludge and fewer loose stones. The one steep wall in Sinister can also be avoided.

While both gullies are a grade 1 scramble, Sinister is more enjoyable and is far more popular.

Don’t be put off by the unusual names; sinister is Latin for left or left side while dexter is Latin for right, or right side (source).

For those of you who have already ascended Sinister, check out the photos and videos of Dexter Gully here.

Route Profile and More Info

Scrambling Grade: Summer Scrambling Grade 1/Winter Grade 2 Climb

Navigation: Literally straightforward once you’re in the gully. The approach could be problematic in poor weather but the gully is easy to follow and short.

Dangers: The steep section three-quarters of the way up is the most obvious hazard. Otherwise, the risks and dangers are as you would expect from a summer grade 1 route (winter grade 2 climb). Some rocks may become slimy in the winter but holds are solid in the summer due to the number of people who use this route.

Approach Time: 1hr 15m max.

Ascent Time: In summer, around 15 mins (exc the Bristly Ridge continuation which is quite an undertaking).

Popularity: Very popular in the summer, the most popular route onto Bristly Ridge.

Fun Rating: 9/10.

My Dislikes: It’s a short gully and over way too soon.

Kit List: My kit list is here.

Similar Routes in Snowdonia: Dexter Gully, Nor’ Nor’ Groove, Seniors Gully, Y Gully, Main & East Gullies, Idwal Staircase, Milestone Gully.


I’ve been up Sinister Gully more times than I can remember and it’s one of my favourite lines.

I initially found this route in a guidebook called “Scrambles in Snowdonia” by Steve Ashton. It was first published back in 1980 but has been updated several times since, most recently in 2017.

If you want a guidebook to take with you on scrambles, this compact book is the best.

Recommended Guide Book:

Scrambles in Snowdonia

Scrambles in Snowdonia by Steve Ashton (#ad)

About Daniel Woodley

This description of Sinister Gully was created by Daniel Woodley, aka The Bald Scrambler.

From walking along beaches and kayaking down rivers to making his way up mountains and even jumping out of planes, Daniel has a love of the outdoors but scrambling is his real passion.


Daniel Woodley

Daniel Woodley aka The Bald Scrambler

Have fun, keep safe. Hopefully I’ll see you on the mountains one day

By The Bald Scrambler

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