Greater London is often referred to as "the City" or "the Square Mile" and it forms the main financial district. Archaically, the urbanised area of London was known as the Metropolis. In common usage, the terms "London" and "Greater London" are usually used interchangeably. Greater London is officially divided for some purposes, with varying definitions, into Inner London and Outer London. For some strategic planning purposes it is divided into five sub-regions. Greater London is under the strategic local governance of the Greater London Authority (GLA). It consists of an elected assembly, the London Assembly, and an executive head, the Mayor of
City of London Ireland. The Corporation owns Old Spitalfields Market and Billingsgate Fish Market, in the neighbouring London Borough of Tower Hamlets. It owns and helps fund the Old Bailey, the Central Criminal Court for England and Wales, as a gift to the nation, having begun as the City and Middlesex Sessions. The City has its own independent police force, the City of London Police—the Common Council (the main body of the Corporation) is the police authority. The rest of Greater London is policed by the Metropolitan Police Service, based at New Scotland Yard. The City has one hospital, St Bartholomew's Hospital, also