City network

City networks are a geographical concept studying connections between cities by placing the cities as nodes on a network. In modern conceptions of cities, these networks play an important role in understanding the nature of cities. City networks can identify physical connections to other places, such as railways, canals, scheduled flights, or telecommunication networks, typically done using graph theory. City networks also exist in immaterial form, such as trade, global finance, markets, migration, cultural links, shared social spaces or shared histories. There are also networks of religious nature, in particular through pilgrimage.

The city itself is then regarded as the node where different networks run together. Some urban thinkers have argued that cities can only be understood if the context of the city's connections is understood.

It has been argued that city networks are a key ingredient of what defines a city, along with the number of people (density) and the particular way of life in cities.