Bryn y Castell is an Iron Age hillfort perched on a small hill in remote moorland above the Roman Road known as Sarn Helen. Excavations revealed the foundations of wooden houses and many stone buildings inside the rampart, as well as the remains of smelting furnaces and iron debris. It was occupied from the late Iron Age until the arrival of the Romans. The hillfort is about one mile up a track that leaves the B4391 just over a mile from Llan Ffestiniog.
