Mam Tor Rushup Edge and Mam Tor are the dramatic high points of the feature known as ""The Great Ridge"" - a dividing line between Castleton and Edale. Mam Tor reaches a height of 1,696 feet and is known as ""The Shivering Mountain"" on account of the instability of its shale layers. Landslips over the years have rendered the old road below the mountain impassable by vehicles. At the top of Mam Tor signs of tremendous ramparts are proof of the vast Iron Age hill fort that once existed here. It is believed that Mam Tor was occupied as early as c1350 BC.