Kevin Lynch, Professor at M.I.T., published The Image of the City. His goal was to identify what features of the built environment were important to the people of the city. Lynch identified five key elements that make up an individual's perception of their city: paths, edges, districts, nodes, and landmarks.
Paths
Paths consist of the "channels along which the observer customarily, occasionally, or potentially moves". These can include streets, paths, transit routes, or any other defined path of movement. It is important to note that the paths an individual identifies may not correspond to a traditional street network. These are often the most predominant items in an individual's mental map as this is main mechanism for how they experience their city.
Edges
Edges provide the boundaries that separate one region from another, the seams that join two regions together, or the barriers that close one region from another. They are linear elements, but are not the paths along with the individual experiences the built environment. They can be physical edges such as shorelines, walls, railroad cuts, or edges of development, or they can be less well-defined edges that the individual perceives as a barrier.
Districts
Districts are "medium-to-large sections of the city". They are typically two-dimensional features, often held together by some commonality. The individual often enters into or passes through these districts. According to Lynch, most people use the concept of districts to define the broader structure of their city.
Nodes
Nodes are points within the city, strategically located, into which the individual enters (and which is often the main focal point to which she or he is traveling to or from). There are often junctions – a crossing or converging of paths. They often have a physical element such as a popular hangout for the individual or a plaza area. In many cases, the nodes are the centers of the district that they are in.
Landmarks
Landmarks are also a point-reference (similar to nodes). However, unlike nodes, which the individual enters during his or her travels, landmarks remain external features to the individual. They are often physical structures such as a building, sign, or geographic features (e.g. mountain). The range of landmarks is extensive, but the commonality is that they are used by the individual to better understand and navigate the built environment.
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