This drawing is rich in archaeological sites, among them the prehistoric monument known as Stonehenge. Situated on Salisbury Plain, it is the most celebrated megaithic monument in England. The iron-age hillfort of Old Sarum is also marked. A castle and cathedral were built on its earthworks during the 12th century, but abandoned when a new cathedral was built a mile and a half away - the foundation of the modern city of Salisbury. The red line extending from Old Sarum to Beacon Hill is the baseline for the triangulation of the area. Several other archaeological sites are marked: the iron-age hillforts at Vispasians Camp, Ogbury Camp and Clorus's Camp.