To see the whole of one city.
My fascination for city maps is a romantic one. It stems from the idea that maps make something visible that cannot actually be seen.
Two hundred years ago it would still have been possible to see the whole of any city in the world with your own eyes. From a high point in the centre you���d see the roofs of houses, towers and churches. You���d be able to see the edges of the city behind the buildings: the trees, fields, streams and lakes of the farmland that surrounded the city and marked its borders.
During the Middle Ages, some 90 per cent of all cities had fewer than 2000 inhabitants. During the 18th century, big American cities like New York, Boston and Philadelphia had populations of no more than 3,000 people.
It was only later, during the 19th century, that cities grew dramatically. London reached a population of one million in 1811 and Paris the same number 30 years later. By the end of the 19th century it had become impossible to see the edges of the city with your own eyes anymore.
It must have been at around this point in history that imaginary and invisible cities were born. Urban sprawls became places of extremes. People started to think and write about big cities as if they were autonomous machines with souls. They would talk about their city as if it were a person it took skill to know.
My fascination with city maps has to do with this imagination of the unseen. A good city map shows opportunities, not streets. To see the whole of one city with your own eyes.