Old Sarum is the site of the earliest settlement of Salisbury, in England. The site contains evidence of human habitation as early as 3000 BC. Old Sarum is mentioned in some of the earliest records in the country. It sits on a hill about two miles north of modern Salisbury.
Old Sarum was originally a hill fort strategically placed on the conjunction of two trade routes and the River Avon, Hampshire.

The hill fort is broadly oval in shape. 400 m (1300 feet) in length and 360 m (1200 feet) in width, it consists of a bank and ditch with an entrance on the eastern side. However, by the 19th Century, the village was officially uninhabited and yet still had formal parliamentary representation, making it the most notorious of the rotten boroughs that existed before the Reform Act 1832.

It is now an English Heritage property and open to the public. The site is located on Castle Road, 2 miles north of Salisbury via the A345.
(Source:Wikipedia.org)