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 previously been dominated by warm seas.  A westward facing chalk spur with a river valley either side provided a naturally defensive site.
Old Sarum marks the eastern boundary of the linear settlement of Stratford sub Castle. There are excellent views of the site from fields and properties along Stratford Road.
Historic England describes the site as
"a multivallate Iron Age hillfort with contemporary settlement outside the ramparts. It also has evidence of Romano-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 much visited." 
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 it under the care of the Secretary of State. Old Sarum is today managed by Historic England on behalf of the Secretary of State.
 British Geological Society Accessed 3 April 2017
 Historic England Accessed 3 April 2017
See also the section on this website about the Old Sarum Landscapes Project - a current Archaeological investigation conducted by the Universities of Southampton and Swansea, in which Stratford sub Castle residents play a part.