Streets are where the needs and values of different users and activities come together. Main streets in the Netherlands were either planned in major urban expansions or developed over time in the shape of ribbons upon dykes—‘long lines’ of continuously active streets. This chapter presents two cases from the Amsterdam metropolitan region: vanWoustraat-Rijnstraat, a main street planned as part of an urban expansion, and Westzijde, a main street that developed over time as part of a long line. While vanWoustraat-Rijnstraat is tightly organised and coherent in both appearance and function, Westzijde is characterised by a multitude of different buildings and functions. This study visualises the spatial-structural qualities that facilitate the evolving economic activities of these two streets. It explores the variation between them by morphological differentiation and determines several spatial characteristics that enable the mix: modularity of the urban plan, complementary ‘front’ and ‘back’ sides, structural coherence and territorial steps between the ‘front’ and ‘back’ sides to buildings, blocks and neighbourhoods.@en