City Hall was constructed at a cost of £43 million on a site formerly occupied by wharves serving the Pool of London. The building does not belong to the GLA but is leased under a 25-year rent. Despite its name, City Hall is not in and does not serve a city (according to UK law), often adding to the confusion of Greater London with the City of London, which has its headquarters at Guildhall and is surrounded by the former. In June 2011, Mayor Boris Johnson announced that for the duration of the London 2012 Olympic Games, the building would be called "London House".