What element of a city does a river represent?

A river in the context of urban design and city planning serves as an edge. This designation stems from the way rivers delineate spaces, influencing the layout and organization of urban areas. An edge is typically a boundary or a barrier within a city, where two different environments meet. In many cases, rivers serve as natural boundaries between neighborhoods, districts, or even different types of land use, creating distinct environments on either side.

By functioning as an edge, rivers can shape the flow of movement and accessibility throughout the city, influencing patterns of development and connectivity. They often define the limit of urban expansion and impact how neighborhoods interact with one another. While elements like paths, nodes, and landmarks also play vital roles in urban geography, the specific defining characteristic of a river as an edge underscores its role in shaping the physical and conceptual boundaries of urban space.