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Location Map ( geo)
Cameraicon.png View gallery (24)
From:  Caernarfon (SH480627)
To:  Capel Curig (SH720581)
Distance:  17.9 miles (28.8 km)
Meets:  B4419, A487, B4366, A4244, A498, A5
Primary Destinations
Highway Authorities

Conwy  • Gwynedd

Traditional Counties


Route outline (key)
A4086 Caernarfon – Capel Curig

The A4086 passes through some of the most memorable and famous parts of Snowdonia in North Wales, and is a popular tourist route. Unlike many 4-digit A-roads, its alignment and routing have hardly changed since road numbers were first allocated in 1922.


Caernarfon - Llanberis

Tan Ralt heading out of Caernarfon

It starts on the B4419 (original line of the A487), Bangor Street in the centre of Caernarfon, but the first section along Poolside is now one-way westbound, so for most traffic the route starts on the A487 at Eagles Junction one block to the east; the A4086 starts on the old main road through town and was not moved when the relief road was opened in 1981. A short run north east along Tanralt leads to another roundabout where the B4366 turns off, and then it winds out of town along Llanberis Road. After pasing between the county courts and fire station, a mixture of commercial premises sit on the left, with houses to the right, most of which are set back behind service roads. The steep wooded valley of the Afon Cadnant then lies down to the left, beyond which modern housing sits opposite the towns large industrial estate. The town's new bypass is then met, with the A4086 slightly realigned to meet the Cibyn Roundabout on the A487.

The route then continues to wind eastwards, dipping down to cross the Afon Seiont at Pont-rug. Just before the bridge, a left turn leads back to the A487, and just after a right turn curves south across the A4085 to the A487 as well. Between them, these roads formed an informal bypass route of the town before the new bypass was built. The route then follows a sinuous route, climbing gently across fields and past scattered buildings to reach the large village of Llanrug. The A4086 follows Llanberis Road through the village, and before long the mountains come into view ahead. The small village of Cwm-y-Glo stands at the foothills of Snowdonia, and is bypassed with the road running along the old trackbed of the Llanberis branch line. A little further on, still on the old railway line, the A4244 is met at a new roundabout, beyond which the road is soon heading into the mountains.

Before long, it resumes its original, albeit improved line for a time as it winds along the wooded shores of Llyn Padarn. The trees obscure much of the view, but glimpses of the hills and lake can be seen here and there. A right turn then leads into the well-known village of Llanberis, where the famous Snowdon Mountain Railway departs towards the summit, while just across the road is the station for the less well-known Llanberis Lake Railway. The village is bypassed with the A4086 once more reverting to the old railway line, which runs along the shore side of the village. Vast car parks are provided to serve the thousands of tourists who visit every year, and there are numerous attractions to see, although the scenery itself is spectacular. As the trees finally peel back, the enormous mounds of slate waste, generated by centuries of quarrying on the hills across the lake, dominate much of the view.

Llanberis - Pen-y-Pass

As the road winds round past the hotel and out of the trees onto the shore of Llyn Peris, the vast scale of quarrying on the northern shore becomes apparent. A dozen or so ledges climb up the mountain side, each higher than a three storey house, and with vast slopes of waste tumbling down on either side. The lake shore is at around 100m, and the highest part of the quarry is above 600m altitude, with ruined buildings and disused inclines being identifiable in many places. This view draws the attention, but the road itself needs attention too, as it winds along a narrow ledge above the lake. There are several small laybys allowing traffic to pause and take in the views of the quarry, and ahead where the road must fight its way into the pass of Llanberis. A sharper right-left takes the road around a bluff as the lake narrows, and then the road drops down to cross the Afon Nant-Peris at the head of the lake.

Llanberis Pass
The A4086 climbing Llanberis Pass

After this, the road starts the climb up the Llanberis Pass into the mountains. Snowdon lies up to the right, and while the summit is never in view, the views of its lower slopes and mountains on all sides can be spectacular if the cloud cover affords it. A series of long sweeping bends leads past the scattered houses of Nant Peris, and then the valley floor gets steadily narrower, the flat fields at the head of the lake giving way to rough hill grazings. The road itself is hemmed in by stone walls, but the whole landscape is constricting, and after passing the last farm, the road is squeezed onto a narrow twisty ledge above the mountain stream. Huge boulders lie strewn across this narrow valley floor, with steep scree slopes rising up to sharp outcrops and cliffs towering above. The landscape is constantly changing, and this is evident by the build up of small fragments of slate and rock behind the roadside wall, occasionally spilling over into the carriageway.

Laybys are provided as often as seems possible, some quite long, as the road continues to wind gently up hill. Higher up the landscape becomes rawer still, the natural slopes looking more and more like the old quarry workings near Llanberis, as the annual cycle of water ingress and frosts continues to shatter the hillsides, creating more scree which suffocates the vegetation. A sharp double bend carries the road back over the infant stream on an old stone arch of Pont y Gromlech just as the valley floor starts to widen once more. a patchwork of tiny fields surrounded by tumble down stone walls now sits between road and river, while the hillside is tumbling down to meet the road to the right instead of the left. Ahead, the road can be seen snaking its way every upwards, curving in around a fold in the hillside before emerging higher up on a long incline supported by some substantial retaining walls, and perhaps a buttress or two.

This snaking ascent finally sweeps around above the head of stream and crosses back to the scree slopes to the north, where a secondary wall a few metres from the roadside seems to be catching the tumbling rocks. At the top of the pass is Pen-y-Pass, home of a youth hostel and café and the start of one of the most popular ways of getting up Snowdon on foot. The summit here is 359m above sea level, making it the highest point a car can get to for people to begin an ascent on Snowdon, and as such there is a vast car park, yellow lines and a clearway in operation. The summit is a short hump between the buildings, before the descent begins, and if you have been lucky enough to climb up without being enveloped in mist, the chances are that the view ahead are hidden behind a white curtain of cloud.

Pen-y-Pass - Capel Curig

The descent is perhaps a little less dramatic overall, although at first the road runs along high on the hillside above a steep valley cut by a plunging stream. Before long, two road lines can be seen ahead cutting across the hillside on the far side of another valley, the upper line being the A498, while the lower one is a much older route. As the A4086 curves in and out along the hillside, the steep drop below the road can be seen from time to time, and as the road curves around into the bigger valley ahead, it is cut into the hillside with rock cliffs rising up to the left. A gentle, sinuous descent on shallower slopes then leads down to Pen-y-Gwryd, about a mile from Pen-y-Pass, where the A4086 reaches a T-junction. Here the route TOTSOs left, with the right-hand road being the northern end of the A498. An old hotel and couple of houses stand on the left as the road winds round a small lake, but soon it opens up and begins a flat and fast drive down the valley of the Nant Grwyd.

This section of the route, in a wide valley between steep mountainsides, has been substantially improved over the years, with numerous laybys showing the older windier route. Fast sweeping bends now lead gently downstream with the river down to the right. A handful of farms can be seen in the valley, those on the far side connected by a small bridge over the river just above the twin lake of Llynau Mymbyr. The winding road comes quite close to the lake shores, and there are now good views ahead into the lower hills on the eastern edge of Snowdonia. A sharper right bend leads, almost unexpectedly, into Capel Curig, where the route has to squeeze between the buildings and car parks of Plas y Brenin, the Welsh national outdoor centre. Remaining twisty, the road winds over the small stone bridge crossing the Afon Llugwy, and ends soon after on the A5 at a T junction opposite the church. Capel Curig is a scattered village, with buildings dotted along the A5 for another mile or so to the west.


The Llanberis Bypass was opened on 14 July 1973 by Geronwy Roberts, MP for Caernarfon. It was built on the route of the former Caernarfon to Llanberis railway, alongside Llyn Padarn, at a cost of £98,000.

Related Pictures
View gallery (24)
Llanberis Pass from the Lip of Cwm Glas Mawr - Geograph - 224637.jpgPre Worboys sign at the entry point of Llanberis - Coppermine - 4707.jpgSAM 0201-min.JPGA4086-lyn-peris.jpgA4086-pen-y-gwryd.jpg
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Earlier iterations: A4008 • A4013 • A4015 • A4020 • A4032 • A4040 • A4041 • A4044 • A4045 • A4047 • A4050 • A4051 • A4052 • A4053 • A4057
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