London is the capital and most crowded city of England and the United Kingdom. Standing on the River Thames in the south-east of the island of Great Britain, London has been a noteworthy settlement for two centuries. It was established by the Romans, who named it Londinium. London's old center, the City of London, to a great extent holds its 1.12-square-mile (2.9 km2) medieval limits. Since in the nineteenth century, "London" has likewise alluded to the city around this center, verifiably split between Middlesex, Essex, Surrey, Kent and Hertfordshire, which today generally makes up Greater London a district represented by the Mayor of London and the London Assembly.