Carl Wark, also known as Carls Work, Charles Work and Carles Work, is an escarpment hill fort near Sheffield, Yorkshire in the middle of Hathersage Moor. It sits 1246 ft above sea level. To the north is the rocky outcrop of Higger Tor with it's collapsing blocks of stone sliding down the hillside, to the east is a slope down to a valley bottom and then the edge of Burbage Rocks while to the southwest is Millstone Edge and a natural balancing rock tor. It is thought to be Iron or Dark age in date but it could well be that use of Carl Wark started even earlier during the Neolithic. Bronze age artifacts have been found close by including cairn, ring cairn and field systems. This helps to show a long general occupation of the area. It is possible it was used by the Brigantes. The area has been used extensively in modern times as a source for mill stones.
Carl Wark uses the very steep natural cliffs around the fort as part of its defenses. The man made wall on the west end of the fort is about 3m in height on the outer side with an earth and rubble bank piled against it on the inner side of the fort. The sheer cliffs rise from a height of 15m to about 25m and surrounded by a very steep bank. Across the shallow neck of the plateau a heavy stone wall has been constructed and this wall is 'L-shaped' and bends around the far side of the fort to form its entrance. It is possible that the hill fort was surrounded by a large circular ditch enclosure of simple construction.
The rocky interior is unlikely to have been the main living location for the fort's occupants - the main village is possibly located somewhere to the south of the main entrance. The whole inner area of the fort covers about one hectare. Earlier Bronze age Cairns and field systems are close by.
A sight-line exists between Carl Wark and the hill fort of Mam Tor about 10 miles to the west. Mam Tor cannot be seen from the south of Carl Wark until one has walked though the entrance and up onto the banks behind the walling when it suddenly appears dark and brooding in silhouette on the horizon.
Carl in Carl Wark translates as a synonym for the Old Man or the Devil.
One historian writing about the area believed that the names Carl and Ygger (Higger Tor) are references to the Norse God Odin.