Abstract
The paper aims to investigate if the changing principles in the protection of historic urban spaces arose as a result of evolving rationale of modern architecture and town planning over the last two centuries. The research was performed using a chronological comparison of the literature, source texts and analyses of graphic materials. Considerations include the concept of beauty of a city upgraded by its reconstruction and conservation, in the perspective of the 19th century great theoreticians representing two different aesthetic attitudes: Viollet-le-Duc and John Ruskin. The theory concerning beauty as an essential value of a city underwent a radical change in the 2nd half of the 20th century. The initial theories were followed by expert groups and institutions resulting in formulating directives and charters, e.g. the Venice Charter. Conventions and regulations concerning the protection of architectural and urban heritage were the achievement of communities, also beyond Europe. They expanded the concept of beauty of a city by the aspect of cultural heritage, taking into account the human being and the role of aesthetic experience (Cesare Brandi). The research reveals a new understanding of historic urban centres. Starting with monuments protection, now conservation encompasses heritage spaces as a whole, implements legal provisions and often influences development of new methods and technologies with social aspect: sustainability and preservation of cultural continuity.