Photograph: Alamy Part of the solutionīut does this mean that density is inherently terrible? At times, it has been closely associated with urban, and moral, decay. View image in fullscreen Hong Kong’s Kowloon Walled City was probably the densest neighbourhood in history, with more than 1,000,000 people per sq km. When the famously lawless walled city was subject to a census in 1987 it had more than 30,000 people living there – a density of well over 1,000,000 people/sq km. This phenomenally dense cluster of 12-storey apartments around a tiny courtyard had alleyways like tunnels and Jumbo Jets swooping directly overhead into the old Kai Tak airport. Probably the densest urban environment humans have ever created was Kowloon Walled City, a block on the Hong Kong mainland which was demolished in the 1990s. Rocinha, the largest favela in Rio de Janeiro, has a density of 48,000 people/sq km and over the years has accumulated much of the infrastructure of the city down the hill, gaining new problems of rising living costs and the threat of gentrification. Kibera, a slum in Nairobi, is infamous for its horrendous poverty and its metal shacks built millimetres away from railway lines, while Dharavi in Mumbai has a reported density of over 200,000 people/sq km. This creates packed neighbourhoods often without political recognition and thus no recourse to protection from crime, drugs, disease, natural disaster, deprivation and lack of education. From the Rookeries of old London, to 20th-century population explosions in favelas and barrios, economic pressure can force the poor into ultra-dense living conditions. People must find places to live, and when there is a strong economic force drawing people with few resources into a city with little regulation, then slums grow. It’s not just about physical restrictions. This led to the canyons of Manhattan – which even today with its huge amount of commercial space has a density of 26,000 people/sq km – and eventually to Hong Kong with its forests of 70-storey housing blocks crowded at the foot of the mountains. By unlocking the third dimension, the skyscraper became possible. Photograph: Courtesy Design Museumīut it was the invention of the lift that really allowed density to rise. View image in fullscreen Dharavi, Mumbai has a reported density of over 200,000 people/sq km. “I believe, this may be said with truth,” he wrote, “that in no city in the world so many people live in so little room as at Edinburgh.” In the early 18th century, the author Daniel Defoe was amazed by the high-rise flats of Edinburgh – sometimes as tall as 12 storeys – teetering over the Royal Mile. Ancient Rome is believed to have reached a population of over 1 million inhabitants (although this figure has been disputed), many of whom were packed into Insulae, apartment blocks rising up to six storeys above shops – an urban form that would not look out of place in contemporary Europe. The effect of this military encirclement still applies today in the besieged Gaza Strip – which is completely blocked in by Israel and Egypt and has the fifth highest population density of any territory on the planet.Īnd then there’s the exploitation of verticality. In Europe, by the end of the 17th century, the ultra-sophisticated, space-hungry bastions and ravelins that surrounded many cities were in danger of strangling life within. From Iron Age hill forts to medieval castles, military protection encouraged populations to huddle together within walls. I believe that in no city in the world so many people live in so little room as at Edinburgh Daniel Defoe, early 18th centuryĪnother cause of density are defensive boundaries. Before it was abandoned and became a hallowed site of modern ruins, the offshore coal mine of Hashima Island near Nagasaki had more than 5,000 people living on an area barely 400 metres long, giving it a density above 83,500 people/sq km. This island effect can lead to real extremes. It doesn’t have super tall buildings or other spectacular architecture, but having to build on all possible scraps of land means it has a density of 23,000 people per sq km. Malé, the capital of the Maldives, is an island city with an area of just 5.8 sq km and a population of more than 130,000 people. Prime among these are natural boundaries. Photograph: Starcevic/Getty Images/iStockphotoīut what causes high density? While the roots of urban growth are complex and interlinked, there are factors that simply force people to live in high-density environments. View image in fullscreen Barcelona is one of Europe’s most densely populated cities.

Hong kong population density map in us