This aerial view of Hanoi, Vietnam, clearly shows areas of decreasing density between the city and the countryside, making it hard to define the limits of the "urban" area.
In everyday usage, terms related to human settlements have vague, shifting meanings. What one person might describe as a small ‘city’ might be a ‘town’ or ‘village’ for someone else; one person’s ‘megacity’ might be a cluster of cities from a different perspective. Similarly, we can usually identify areas that are clearly within a city and others that are outside it, but there is usually a peri-urban area of intermediate density that usually lies between the two, making it hard to define a clear city limit. Formal administrative boundaries may have historic or political meaning, but are rarely aligned with the physical or economic extents of the urban area.
What exactly is a city? It depends who you ask
It turns out there is no standard international definition of an ‘urban’ area or ‘urban’ population. Each country has its own definition, and collects data accordingly. The statistic that 50% of the world’s population is urban is arrived at simply by adding up these incomparable, and sometimes conflicting, definitions.
A recent EASIN Urban, Transport and DRM Community of Practice (CoP) meeting I attended in Seoul, South Korea was an eye opener in terms of the rapid urban development of the city of Seoul. Considered an East Asian tiger, manufacturing and an export-led economy have made Seoul a global city with neon skylines and the new focus of Asia’s technology boom. A presentation by Seoul Metropolitan Government (SMG), the agency responsible for the city’s urban planning, describes the city as a ‘strategic space for people to reside in since ancient times’. Nevertheless, the city and its urban identity have gone through various transformations – through the Japanese occupation (1910-1945) to restoration after the Korean war (1950-53) to industrialization (1960s-1970s) to development and globalization. In SMG’s words, Seoul is witnessing the ‘environmental and historical awakening as a world city’. Evidence of this was seen in sites I visited to the restored Cheonggyecheon stream and a former landfill converted to Haneul Park.