The building fabric is a crucial component of cities. Buildings address some fundamental human needs by providing spaces for living, working and leisure. However, the main aspects of building fabric are influenced by a structure that is invisible to most of us—the ground plan. Indeed, the size and volume of a building are shaped by its two-dimensional arrangement on the ground, the size and shape of the plot it occupies, and the street it faces. A fundamental element in this interplay between ground plan and building fabric is the street section. The street section, defined by the ratio of building height to street width, establishes the structural framework for subsequent key decisions, such as the definition of ground floors and the placement of doors and windows. Indeed, the street section offers the framework for street life. Another important aspect is how the ground plan and building fabric change over time. Urban landscapes are subject to the many, and sometimes conflicting, strategies and actions of different agents, creating a constant tension between conservation and transformation. The ground plan influences the adaptability of the urban landscape and determines which elements are most likely to undergo change.