The City, also known as the Square Mile, (2.9km2), is the small historic core of London whose boundaries have remained little changed since the 3rd century when the Roman’s built London Wall, a defensive wall around Londinium, their AD43 trading and financial community.
During Roman times it was the site of the largest Roman amphitheatre in Britain, remains of which are on public display in the basement of the Guildhall Art Gallery. A black circle marking the outline of the roman arena is painted on the courtyard in front of Guildhall.