The B4418, which runs up Dyffryn Nantlle, is the hidden gem of Snowdonia’s mountain roads. This superb col gives a good challenge from the west and has a similar feel to the Llanberis Pass side of Pen y Pass. It is rugged, steep-ish, but with undulations so you can recover, yet steep enough to feel like you’re expending energy for a good cause. The views across the mountain landscape are stunning and there is a wonderful sense of remoteness.
If you’re doing a long ride from the south it provides a very satisfying finish, taking you away from the flat roads near the coast. It also makes a great loop from Waunfawr for a shorter ride.
The descent into Rhyd Ddu is good and fast with some dips to get you out of the saddle and sprinting to keep your momentum going. Watch out as you enter Rhyd Ddu itself - you can be travelling quite fast and the road suddenly narrows as you enter the village; oncoming traffic tends to be in the middle of the road too.
Taken east to west it’s a steeper, tougher climb. The descent also is good, but with some blind bends.
The high point of the col at Bwlchgylfin is only 236m; nonetheless it is in a very mountainous area so it is occasionally blocked with snow during the winter months.
The normal starting points are either Nantlle or Rhyd Ddu (depending on the direction of ascent), or further away if you are completing a longer route.