Beyond the river rises Caer Drewyn. The stone wall encloses a large area on a steep slope. It does not occupy the summit of the hill, but a spur near a spring from which flows a tiny rill. The walls were of stone unset in mortar, and they have fallen and form a continuous mound of débris. Within are a few ruined _cytiau_. The camp is of the type of the Irish forts near the coast, but has been supposed to be earlier and to belong to the Bronze Age, and without an exploration with pick and shovel there is no determining its period, for much the same construction belonged to both epochs. It was occupied at a much later time. Owen Gwynedd in 1164 rose in revolt against Henry II. The English King collected a mixed force, and from Oswestry ascended the Dee. Owen and his brother Cadwaladr of Merioneth fought a battle with him at Crogen, near Chirk. The King’s life was saved by the self-devotion of Hubert de Clare, who, seeing an arrow hurtling through the air towards his master, interposed his body, and received the missile in his breast. The Welsh retreated across the Berwyn Mountains to Corwen, pursued by the English, and Owen established himself and his forces within this venerable ring of stones. They could obtain plenty of mutton from the mountains and moors at their back, and there was water in the spring under the north wall. Henry’s army camped on the opposite hill. The weather broke up, rain poured down, and the ground of the English camp became a quagmire. The English dared not venture far for fear of falling into ambushes among the woods and rocks, and suffered for want of food. Men and horses dwindled through sickness and privation. Military stores ran short, and at length, in the mood of a baffled tiger, Henry was compelled to withdraw without having accomplished the end aimed at in this campaign. Raging at his discomfiture, he had the eyes torn out of the heads of the sons of Owen Gwynedd and Rhys ab Tewdwr, whom he held as hostages. Rûg, near Corwen, is the scene of the treacherous seizure of Gruffydd ab Cynan, king of Gwynedd, in 1080, by Hugh the Fat, Earl of Chester. He invited the king to come unattended and unarmed to a friendly conference here, and when he arrived had him loaded with chains and carried off to Chester, where he remained a prisoner for twelve years. He owed his release to a young man of Corwen, who on some plea obtained access to him in prison, and carried him forth on his back, chains and all, on a night when the garrison was keeping high revel and his guards were drunk. On his return into Gwynedd, he lurked for some time among the mountains till he had rallied sufficient men about him, when he swooped down on castle after castle of the Normans, took and burnt them and drove the invaders out of his lands.