Open Space: Transparency - Freedom - DematerialisationThe aim of the study is to analyse and describe in detail one of the most important trends in architecture in the 19th and 20th centuries: the evolution leading from the closed, hermetic spaces of the early cultures and the Middle Ages to the "open space" and transparency of the 19th and 20th 21st centuries. Historically, the focus is on the "diaphanous" space of the Gothic cathedral, the opening of the late Baroque dome towards the sky, the