During the Renaissance, the five senses were understood to form a hierarchical system from the highest sense of vision down to touch. Vision was correlated to fire and light, hearing to air, smell to vapour, taste to water, and touch to earth.
Perhaps the human fascination with fire stems from the totality of its sensory stimulation. The fire gives a flickering and glowing light, ever moving, ever changing. It crackles and hisses and fills the room with the smells of smoke and wood and perhaps even food. It penetrates us with its warmth. Every sense is stimulated and all of their associated modes of perception, such as memory and an awareness of time, are also brought into play, focused on the one experience of the fire. Together they create such an intense feeling of reality, of the "here and nowness" of the moment, that the fire becomes completely captivating.
The contents of the city's images which are referable to physical forms can conveniently be classified into five types of elements: paths, edges, districts, nodes, and landmarks.
Paths are the channels along which the observer customarily, occasionally, or potentially moved.
Edges are the linear elements not used or considered as paths by the observer. They are the boundaries.
Districts are the medium-to-large sections of the city, conceived of as having two-dimensional extent.
Nodes are points, the strategic spots in a city into which an observer can enter, and which are the intensive foci to and from which they are traveling.
Landmarks are another type of point-reference, but in this case the observer does not enter within them, they are external. They are usually a rather simply defined physical object: building, sign, store, or mountain.