A megacity, a metropolis, a megalopolis and a global city: what’s the difference?
Modern civilization is impossible without cities. They vary in culture, size and different institutions, moreover, certain areas become more significant throughout the development of a region. Historically, the size or population of a settlement was a general indicator of its importance — the biggest city, the more power it has got. However, with the large rural-to-urban migration during the last century, it has become more difficult to define what makes the city important. Nowadays, there are many types of urban landscapes and it is very important for architects, and designers to classify settlement types effectively in order to successfully develop designs and city plans. The following list provides four keys of definition that have been formed in the last century.

Megacity
Definition ‘megacity’ is used to describe cities with a certain amount of inhabitants. The term was first documented by the University of Texas in 1904. However, the definition has some ambiguity as different organizations suggest different criteria. The most widely accepted definition is that megacity is a city with over 10 million inhabitants and also, with a population density of 2000 people per square kilometer.
New York was the first megacity with modern standards which had reached the 10 million population mark by 1936. The early trend shows many of these cities appeared in traditionally developed areas. However, in recent years, something has recently changed. Almost 70% of the current 47 megacities are found in Asia, and this figure is likely to increase in the coming years as the global movement into urban areas, is very high in these countries. Today, the top five most populated cities are Tokyo, Shanghai, Jakarta, Delhi and Seoul.

Metropolis
A metropolis, that is ‘mother city’ for Greek, was initially the place from where settlers were sent to colonize other areas. Since that time it has developed into a descriptive term for large cities that are key centers of national and regional socio-economic activity, sharing many of the same characteristics with a global city.
However, these two terms vary due to the smaller emphasis a metropolis places on international significance. Such cities have lower standard of living, development and infrastructure. As a result, a global city is always a metropolis – but a metropolis isn’t guaranteed to be a global city. Cairo and Lagos are the best examples.

Megalopolis
A cluster of well-networked cities is called a megalopolis. This term was first used in the early 20th century. Such cities can occur because of variety of reasons: geography can play a large role in the location of megalopolises as well as good international and regional transport links. The subsequent economic growth of one city can have a positive impact on neighboring locations. One of the first examples of the megalopolis was the north-eastern coast of the USA from Boston to Washington. However, there are more of these regions developing in Asia than anywhere else right now such as the Pearl River Delta in China and the Unified Jakarta-Bandung metro area in Indonesia.

Global City
Its first definition was described in 1886. Due to the modern idea of globalization, ‘global city’ as a term was popularised by Saskia Sassen in 1991 when the cities of London, Tokyo and New York served as the prime examples. Till now, these cities are key locations within the world economy, acting as crucial centers for the global trading of goods and services.
Not strictly dictated by population or size, it is sometimes difficult to quantify what makes a global city, but there are several unifying characteristics. Economically, they must serve a variety of international economic services and host the headquarters for several multinational corporations. Socially, it must have a high diversity of cultures, religions, ideologies and languages. There are several cities that were once global and now are not (like Liverpool), and several whose importance is increasing, for example Shanghai.