London is the capital of and largest city in England and the United Kingdom, with the largest municipal population in the European Union.[7][8] Standing on the River Thames in the south-east of England, at the head of its 50-mile (80 km) estuary leading to the North Sea, London has been a major settlement for two millennia. Londinium was founded by the Romans.[9] The City of London, London's ancient core − an area of just 1.12 square miles (2.9 km2) and colloquially known as the Square Mile − retains boundaries that follow closely its medieval limits.[10][11][12][13][14][note 1] The City of Westminster is also an Inner London borough holding city status. Greater London is governed by the Mayor of London and the London Assembly..