Circle in Space-Space in Circle: A Study of Ratio between Open Space and Built-Up Area in Historical Circular Objects

Many cities nowadays explore different circular designs as new sustainable city concepts in different urban aspects. The new trend, as part of the adaptation for climate change, is a strategy of increasing the number of urban open spaces, and circular plan design could be a sustainable approach to urban development. This paper provides a historical overview of various examples of circular objects containing built structures and open spaces from the Neolithic to the present. The Built-Up Area (BUA) and Open Space (OS) relationships are shown histogramically for 36 objects arranged chronologically. The morphospace analysis was performed to determine any possible regularity in the relationships of parts of circular objects. For the purpose of this research, three variables were chosen. First, all selected historical examples of circular objects were divided into two main categories: objects with a total diameter smaller than 300 m and objects with a total diameter bigger than 300 m. Additionally, the selected circular objects were divided by their type of open space to better understand their spatial position. The largest number of analyzed objects belongs to the Parks-Gardens category, followed by settlements, and then earth works, sacral objects and circular buildings, with the smallest number of circular objects being in the category of allotments and plazas. The second variable was Jam area and % of Jam. The buildings are of different sizes up to several hundred m(2), and the areas range up to several hundred ha. The total area to OS ratio ranges from 0% (for Large Serdab) to 100% (for multiple objects). There is a similar situation with the diameter ratios (total and "jam"). Additionally, the final variable was the historical position of the selected circular objects. Circular objects belong to all historical periods from the Neolithic to the present. The aim of this research was to explore the relationship between OS and BUA in various circular objects with different diameters of open spaces and find out if there was any regularity in this relationship. The morphospace analysis of this research indicates that there is no clear regularity in the relationship between the built-up area and the open space, but the aspects and research results shown here contribute to sustainability since the circular design approach could play a key role in future circular design processes.