We all think we know what the word 'city' means - but do we really? In Britain a city traditionally signifies a town, of any size, with a cathedral. So London today includes two cities - those of London and Westminster. But St. Asaph in North Wales, with a population of fewer than 4000 (3491 - Census 2001), is a city with a cathedral. And because of its sheer size, Birmingham was specially made a city in 1889, despite having no cathedral then.
In Australia, a city is simply an administrative district. Here lies Mount Isa, the world's largest city by area, spreading over 40 978 sq km (15 822 sq miles)
In the USA, 'city' is purely a legal term no matter how large or insignificant the township concerned. The US Census, however, terms any place with a population over 2500 as a city, no matter how rural. (By contrast, Kidlington in England, with a population of 17 500, is officially a village, because it is run by a parish council.)
So what is a city? It all depends, it seems, on where you live.