## 1 Introduction  
The importance of public space in urban areas for social activities and human wellbeing is commonly promoted amongst academia, civil society, and urban planning professionals [1; 2; 3; 4; 5; 6; 7; 8]. The definition of public spaces (both conceptually and physically), however, can be a subject of constant debate that is often underpinned by local politics, ownership, and management [9; 10; 11; 12; 13]. Generally public space is understood to include places that are essentially open to the public. This ranges from outdoor open spaces such as parks, gardens, squares, and streets to indoor enclosed places like cafes, museums, libraries and malls, as well as virtual spaces that people increasing access through technological advances [14; 15; 16]. Time spent in public space is an integral component of daily life for urban dwellers. Although the personal benefits derived from public space have been widely discussed, previous studies mostly focused on the dimensions of physical health. This included benefits such as access to fresh air and opportunities for physical exercises that can reduce cardiovascular diseases and obesity [17; 18]. As researchers continue to point out how the body and mind connect and work together for health outcomes [19; 20], it is important to also understand the role of public space in mental health and overall wellbeing. There is a growing body of literature demonstrating how the built environment affects mental health [21; 22; 23]. Increased social interactions and social support are distinct values that benefit mental health and can be positively affected by public spaces. Some examples of these benefits include: the restorative and healing effects provided by greater access to greenery and water [24; 25; 26]; improved physical accessibility and visual permeability of the front-yard for community building [27]; a strengthened sense of community and belonging produced by active public spaces in local neighborhoods [27; 28]; opportunities for relaxation and social exchange provided by privately owned public space (known as POPS) [29] and \"a home away from home\" [30], as well as \"commercial social support\" [31] provided by \"third places\" for people who go there. These few examples underline how the physical and social environment influences how people feel and interact, which in turn impacts people's health and wellbeing. Loneliness is not a new phenomenon, but there is increasing concern that it is a growing problem around the world that poses a severe threat to public health and wellbeing and may be reaching historic levels in some countries [32; 33; 34]. The negative effects of loneliness range from decreased function of the immunity system and increased anxiety and depression to growing levels of early mortality [35], suicide [36], and violence [37]. These effects are physical, mental, and physiological, and also often attached to a fear of being stigmatized by admitting to others feelings of loneliness. A core driver of loneliness is the subjective experience of having a deficit of desired social relationships. The (built) environment, and particularly public space, provides a setting where social encounters, interactions, and activities occur. It is highly plausible to assume that social encounters play a role in enabling social relationships to grow or be formed, and that deepening or expanding social relationships can lessen or mitigate feelings of loneliness. This paper builds upon these assumptions to hypothesize that public space can have an impact on social encounters, which in turn impacts on social relationships, and could have an impact on loneliness in urban populations.