Llyn Arenig Fawr and Y Castell up Arenig Fawr: route map, distance and time
854 m · Snowdonia
Arenig Fawr is a rugged mountain west of Bala, with a memorial on its summit to the crew of an American bomber that crashed there.
A hard mountain walk to the summit from Arenig mountain-path entrance on minor road.
Llyn Arenig Fawr and Y Castell starts at about 342 m and gains 501 m over 4.9 km to 822 m on the track. The first 2 km are the easy part, averaging 3%. The steepest kilometre is the one ending at 3 km, which climbs 160 m at an average of 16%, with a 500 m stretch from 2.7 km at about 34%. It keeps climbing at 11% to the top. About 17% of the way is steeper than 1 in 5, so expect hands-on-knees going and a slow descent.
Llyn Arenig Fawr and Y Castell at a glance
| Distance | 4.9 km one way, to the top |
|---|---|
| Ascent | 540 m |
| Climb on the track | 501 m up, 23 m down on the way |
| Start and top of the track | 343 m to 822 m (summit 854 m) |
| Steepest 500 m | About 34%, from 2.7 km |
| Steeper than 1 in 5 | 17% of the way |
| Time up | 1h 55m by Naismith's rule |
| There and back | 2h 50m, down the same way |
| Grade | Hard |
| Start | Arenig mountain-path entrance on minor road |
| Start grid reference | SH 845 395 |
| Summit grid reference | SH 827 369 |
| Parking | No checked car park for this start; find lawful parking nearby |
Llyn Arenig Fawr and Y Castell map
The track from the start (green) to the summit (blue), with a marker at each kilometre.
Height profile and getting to the start
Near the start
From OpenStreetMap, within 2 km. Check opening times before you rely on them.
Download the Llyn Arenig Fawr and Y Castell GPX
Ascent only: plan your way down. A planning track, not checked on the ground; it doesn't show safe scrambling moves. Track data © OpenStreetMap contributors (ODbL), heights from a terrain model.
Llyn Arenig Fawr and Y Castell kilometre by kilometre
Height, climb and average gradient for each kilometre of the track, with a grid reference at the end of each one to check your position on the map.
| At | Height | Climb | Gradient | Grid ref |
|---|---|---|---|---|
| 1 km | 427 m | +85 m | 8% | SH 848 387 |
| 2 km | 402 m | -25 m | -2% | SH 850 378 |
| 3 km | 562 m | +160 m | 16% | SH 842 373 |
| 4 km | 725 m | +163 m | 16% | SH 833 373 |
| 4.9 km | 822 m | +96 m | 11% | SH 827 369 |
How long Llyn Arenig Fawr and Y Castell takes
| Pace | To the top | There and back |
|---|---|---|
| Brisk 6 km/h, 8 min per 100 m up | 1h 30m | 2h 20m |
| Steady (Naismith) 5 km/h, 10 min per 100 m up | 1h 55m | 2h 50m |
| Relaxed 4 km/h, 12 min per 100 m up | 2h 20m | 3h 30m |
Times leave out stops. Coming down the same way, the table counts the ascent once; steep descents on rough ground can be as slow as the climb.
- Today: sunrise 07:46, sunset 18:13. Start by 14:23 to be down before dark, allowing 2h 50m for the walk and an hour for stops.
- Tomorrow: sunrise 07:48, sunset 18:11. Start by 14:21 to be down before dark, allowing 2h 50m for the walk and an hour for stops.
Arenig Fawr summit weather for this route
There is no recent summit forecast cached for Arenig Fawr right now. The main Arenig Fawr page loads the live forecast when you open it. Open the live Arenig Fawr forecast.
Before you go, also check: MWIS Snowdonia forecast · Met Office mountain forecast.
About Arenig Fawr
Arenig Fawr is a rugged mountain west of Bala, with a memorial on its summit to the crew of an American bomber that crashed there. More about Arenig Fawr, with the live forecast.
On the lists: Hewitt, Nuttall, Marilyn.
Extend the walk: tops near the summit
- Arenig Fawr South Top (837 m), 0.3 km south
- Arenig Fawr South Ridge Top (714 m), 1 km south
- Moel Llyfnant (751 m), 2.6 km south-west
Challenges that include Arenig Fawr
More walks from Arenig mountain-path entrance on minor road
Routes in Peakify's guides that start within 500 m of this one, for another day from the same car park.
- Llyn Arenig Fawr and Y Castell up Arenig Fawr South Top
- Llyn Arenig Fawr and Y Castell up Arenig Fawr South Ridge Top
- Arenig Fawr and southern tops traverse up Moel Llyfnant
Other routes up Arenig Fawr
| Route | Distance | Ascent | Time up | Grade |
|---|---|---|---|---|
| Arenig via Llyn Arenig Fawr | 3.4 km one way | 444 m | 1h 25m | Moderate |
| Arenig quarry and northern ridge | 4.9 km one way | 530 m | 1h 50m | Hard |
In an emergency
Call 999, ask for the police and then mountain rescue. Give your location (the start is at SH 845 395, the summit at SH 827 369), what happened and how many are in your group. If you have no signal for a call, a text to 999 works once you have registered your phone with emergencySMS: text "register" to 999 before you go.
Llyn Arenig Fawr and Y Castell: questions and answers
How far is Llyn Arenig Fawr and Y Castell?
Llyn Arenig Fawr and Y Castell is 4.9 km one way to the summit of Arenig Fawr, with 540 m of ascent. There and back by the same way is about 9.8 km.
How long does Llyn Arenig Fawr and Y Castell take?
About 1h 55m to the summit of Arenig Fawr and 2h 50m there and back by Naismith's rule (5 km/h plus 10 minutes per 100 m of ascent), before stops. A relaxed group takes nearer 3h 30m for the round trip.
How steep is Llyn Arenig Fawr and Y Castell?
The steepest 500 m averages about 34%, starting 2.7 km from the start, and 17% of the way is steeper than 1 in 5. Llyn Arenig Fawr and Y Castell climbs 501 m in all on the track.
Where do you park for Llyn Arenig Fawr and Y Castell?
Llyn Arenig Fawr and Y Castell starts from Arenig mountain-path entrance on minor road. The grid reference is SH 845 395. No checked car park for this start; find lawful parking nearby
Is Llyn Arenig Fawr and Y Castell suitable for beginners?
Not as a first mountain. Peakify grades it Hard: steep, rough ground where a slip matters. Build up on an easier route first, such as Arenig via Llyn Arenig Fawr.
What time should I start Llyn Arenig Fawr and Y Castell today?
By 14:23 at the latest. Sunset on Arenig Fawr today is 18:13, Llyn Arenig Fawr and Y Castell takes about 2h 50m there and back, and that leaves an hour for stops. Start earlier in winter or if the forecast turns.
Is there a GPX for Llyn Arenig Fawr and Y Castell?
Yes. Download it from this page. It is an ascent-only planning track from the start to the summit, plotted on OpenStreetMap paths and not checked on the ground.