Situated 2 miles NNE of Salisbury, Old Sarum is a prominent feature within the landscape. The bedrock here was formed approximately 71 to 81 million years ago in the Cretaceous period, the local environment having been previously dominated by warm chalk seas . A westward facing chalk spur with a river valley either side provided a naturally elevated defensive site.
Photo attrib Google Earth accessed 5 April 2017
The monument of Old Sarum was first scheduled on 7 August 1916 and its current schedule under the Ancient Monuments and Archaeological Area Act 1979 puts in under the care of the Secretary of State.
Old Sarum is managed by Historic England who describe the site as "a multivallate Iron Age hillfort with contemporary settlement outside the ramparts. It also has evidence of Roman-British occupation and documentary evidence of a Saxon burgh and mint. During the medieval period it was rebuilt as a royal motte and bailey castle and includes a cathedral and bishop's palace with an ecclesiastical precinct together with extra-mural settlement remains. The remains of the castle and cathedral are Listed Grade 1. ...The monument is open to the public and is much visited. " 
During the 20th century a number of archaeological excavations were carried out within the monument. The castle, the cathedral and other ecclesiastical buildings within the outer bailey were excavated over a number of seasons between 1909 and 1915 by W H St J Hope, W Hawley and D H Montgomerie for the Society of Antiquaries of London. Further excavations were carried out by J Musty and P A Rahtz in the 1950s.
Starting in the spring of 2014, Old Sarum and the area around Stratford sub Castle has been the subject of a research project undertaken by the University of Southampton Archaeology Department. This project was still active in April 2017. 
 http://mapappps.bgs.ac.uk Accessed 3 April 2017
 https://www.historicengland.org.uk/listing/the-list/list-entry/1015675 Accessed 3 April 2017
 http://www.southampton.ac.uk/archaeology/research/projects/old_sarum_and_stratford_sub_castle.page Accessed 7 April 2017