Perugia, City Walls and Green Areas: Possible Interactions Between Heritage and Public Space Restoration

Black crusts and biological colonisation are among the most common types of ‘diseases’, with diverse aetiologies and presentations, affecting masonry architectural heritage. Over the past decades, there has been an increase in the incidence of this degradation phenomena due to the increase in pollution and climate change, especially on the urban walls of ancient cities. In particular, the present research examines the state of conservation of the city walls of Perugia, which are divided into two main city walls dating back to the Etruscan and Medieval periods and are recognised as historical heritage of high identity and cultural value. The degradation reflects, in the mentioned cases, on the liminal public and green areas. A view is also reflected in local journalism and social media, where residents and visitors have framed the spontaneous growth of herbs and medicinal shrubs within the stone joints of historic walls as an apparently benign and aesthetically pleasing occurrence. This misleading interpretation, while rooted in a superficial aesthetic appreciation, nevertheless draws attention to a real and urgent issue: the pressing need for systematic maintenance and intervention strategies—coordinated between academics, students, designers and stakeholders—which are able to reposition the city walls as central agents of urban and cultural regeneration, rather than peripheral remnants of the past.