Carl Wark Fort (Scan from 1989)

“Carl Wark (sometimes Carl's Wark) is a rocky promontory on Hathersage Moor in the Peak District National Park, just inside the boundary of Sheffield, England. The promontory is faced by vertical cliffs on all but one side, which is protected by a prehistoric embankment. The cliffs and embankment form an enclosure that has been interpreted as an Iron Age hill fort, though the date of construction and purpose of the fortifications remains unknown. The site is a scheduled monument.”
en.wikipedia.org/wiki/Carl_Wark