The Republic of Korea has the highest suicide rate of older population among OECD countries, and depression is the prevailing factor. While it is well-known that the urban physical environment affects mental health, research on the physical characteristics of spaces remains limited. This study aims to explore relationship-oriented space characteristics that can form social networks and reduce depressive symptoms in older adults. After analyzing the differences in social interaction spaces between high-density and low-density areas for older adults in Seoul, we identified social interaction spaces (parks and traditional markets) that are frequently used based on on-site interview results. Two areas were selected for the questionnaire surveys. The main findings revealed that older adults living in areas with diverse spatial planning and close physical relationships between parks and traditional markets, convenient pedestrian environments, and lower population density of older adults had better social networks and lower depressive symptoms. More significantly, the physical characteristics of parks and traditional markets (convenient accessibility, maximized visibility, connectivity, and territoriality) significantly facilitate social interactions. Those engaging in social interactions within these spaces exhibited significantly better social networks and lower depressive symptoms. These findings underscore the importance of considering relationship-oriented space characteristics in spatial and urban planning.