The City of London is a small area within Greater London, England. It is the historic core of London around which the modern conurbation grew and has held city status since time immemorial. The City’s boundaries have remained almost unchanged since the Middle Ages, and it is now only a tiny part of the metropolis of London. It is often referred to as the City or the Square Mile, as it is just over one square mile (1.12 mile² / 2.90 km²) in area. These terms are also often used as metonymies for the United Kingdom's financial services industry, which has historically been based here.
In the medieval period, the City was the full extent of London. The term London now refers to a much larger conurbation roughly corresponding to Greater London, a local government area which includes 32 London boroughs as well as the City of London, which is not one of the 32 London boroughs. The local authority for the City, the City of London Corporation, is unique in the United Kingdom, and has some unusual responsibilities for a local authority in Britain, such as being the police authority for the City. It also has responsibilities and ownerships beyond the City's boundaries. The Corporation is headed by the Lord Mayor of the City of London, a separate (and much older) office to the Mayor of London.
The City is today a major business and financial centre, ranking on a par with New York City as the leading centre of global finance; in the 19th century, the City served as the world's primary business centre. The City has a resident population of approximately 8,000, but around 340,000 people work there, mainly in the financial services sector. The legal profession form a major component of the western side of the City, in and around the Inns of Court, of which two - the Inner and Middle Temples - fall within the City of London boundary.