This is an extract from the book by Kevin Lynch 'The image of the city'. These are the categories of direct interest in design, since they describe qualities that a designer may operate upon.

A spacial region could only be experienced, as a patterned play of spacial changes, by a rather protracted journey through it. Perhaps the processional courts of Peking, or the canal spaces of Amsterdam have this quality. Presumably they evoke an image of great power.

Motion awareness: the qualities which make sensible to the observer, through both visual and kinesthetic senses, his own actual or potential motion. Such are devices which improve the clarity of slopes, curves, and interpenetrations; give the experience of motion parallax and perspective; maintain consistency of direction or direction change; or make visible the distance interval. Since a city is sensed in motion, these qualities are fundamental, and they are used to structure and identify, wherever they are coherent enough to make it possible. These qualities reinforce and develop what an observer can do to interpret direction or distance, and to sense form in motion itself.

Continuity: continuance of edge or surface; nearness of parts; repetition or rhythmic intervals; similarity, analogy or harmony of surface, form or use. These are the qualities that facilitate the perception of a complex physical reality as one or as interrelated, the quality which suggest the bestowing of single identity.

Directional Differentiation: asymmetries, gradients, radial references which differentiate one end from another (as on a path going uphill, away from the sea, and toward the center); or one side from another ( as with buildings fronting a park); or one compass direction from another ( as by the sunlight). These qualities are heavily used in structuring on the larger scale.

Visual Scope: qualities which increase the range and penetration of vision, either actually or symbolically. These include transparencies (as with glass or buildings on stilts); overlaps (as when structures appears behind others); vistas and panoramas which increase the depth of vision (as on axial streets, broad open space, high views); articulating elements (foci, measuring rods, penetrating objects) which visually explain a space; concavity (as of background hill or curving streets) which exposes father objects to view; clues which speak of an element otherwise invisible (as the sight of activity which is a characteristic of a region to come, or the use of characteristic detail to hint at the proximity of another element). All these related qualities facilitate the grasping of a vast and complex whole by increasing, as it were the efficiency of vision; its range, penetration, and resolving power.

Time series: series which are sensed over time, including both simle item by item linkages, where one element is simply knitted to the two elements before and behind it (as in a casual sequence of detailed landmarks), and also series which are truly structures in time and thus melodic in nature (as if the landmarks would increase in intensity of form until the climax point were reached). The former (simply sequence) is commonly used, particularly along familiar paths. Its melodic counterpart is more rarely seen, but may be most important to develop in the large, dynamic, modern metropolis.