Mynydd Mawr is best known for its expansive views towards Snowdon over Llyn Cwellyn. Tucked away on its flanks are two contrasting crags. Sentries Ridge is on the south side and has two excellent ridges. Hidden away on the northeast corner is Castell Cidwm which by way of contrast is one of the most fearsome crags in North Wales. Sentries Ridge will give good climbing in clear weather and dries quickly although it is exposed to the elements. Castell Cidwm faces southeast but is tucked into a gorge and dries slowly. It also seeps after rain particularly the imposing corner of the route Dwm.