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, though remains a notable part of central London. These terms are also often used as metonyms 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. 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. Today it is included wholly in the Cities of London and Westminster constituency, and statute requires that it not be divided between two neighbouring areas.
The City's population fell rapidly in the 19th century and through most of the 20th century as people moved outwards to London's vast suburbs and many houses were demolished to make way for modern office blocks. The largest residential section of the City today is the Barbican Estate, constructed between 1965 and 1976. Here a major proportion of the City's population now live. The Museum of London is located here, as are a number of other services provided by the Corporation.
The City, like many areas of London and other British cities, fell victim to large scale and highly destructive aerial bombing during World War II, in what is known as The Blitz. Whilst St Paul's Cathedral survived the onslaught, large swathes of the City did not and the particularly heavy raids of late December 1940 led to a firestorm called the Second Great Fire of London. However the boundaries of the City of London no longer coincide with the old city wall, as the City expanded its jurisdiction slightly over time. During the medieval era, the City's jurisdiction expanded westwards, crossing the historic western border of the original settlement - the River Fleet - along Fleet Street to Temple Bar. The City also took in the other "City bars" which were situated just beyond the old walled area, such as at Holborn, Aldersgate, Bishopsgate and Aldgate. These were the important entrances to the City and their control was vital in maintaining the City's special privileges over certain trades.
The walls have almost entirely disappeared, although several sections remain visible. A section near the Museum of London was revealed after the devastation of an air raid on 29 December 1940 at the height of the Blitz.