The two big centers of the humanistic towns of Castiglione Olona (from 1421) and of Pienza (from 1462) clear the way for a phenomenon which in the middle of XVIth century founds its coding in Sabbioneta (from 1554). A side from this important cases there are many various ones which travel along the century and often suggest methodological questions: ideal cities or simple high quality projects on an architectural and urban scale? Innovative districts or real urban inventions? The paper proposes both a chronological and typological seriation and an enounciation of methodological criteria for the identification and the highlighting of the peculiarities proper of this chronological phase, partially different from what achieved in the second half of the XVIth century.