Conceived as a theater and emphasizing the decorative space as much as the buildings surrounding it, the piazza satisfies the need of Mediterranean peoples to conduct their lives in the open air.
The defining feature of the piazza is its oppressive roof. 
mnli hypothesis: The defining feature of the piazza is its oppressive roof.  premise: Conceived as a theater and emphasizing the decorative space as much as the buildings surrounding it, the piazza satisfies the need of Mediterranean peoples to conduct their lives in the open air.