Adult day-care facilities, as one type of the care facilities for older adults and people with dementia (PWD), have attracted attention from researchers and practitioners since the 1990s. These care facilities provide community-based programs to meet the needs of older adults during the work day and relieve informal caregivers from the stress of full time care. However, studies that emphasize on architectural environment, and its impacts on the behavior of the care recipients, i.e. the people who use the day-care services, are still lacking. The aim of this study is to offer an insight into the behavior of PWD in adult day-care facilities from an architecturally disciplined perspective, as well as to interpret the relationships between behaviors and architectural properties in order to improve the future facility design. To reach this goal, the study was developed through a strategy that includes two focuses: 1. Focus on the spatial distribution of unstructured behavior of PWD, 2. Focus on the architectural properties including the function complexity, the typology, and the interior furniture. Six day-care centers in Dresden, Germany, were chosen for the case studies. In each center, care recipients over 65 years and diagnosed with dementia by their general practitioners, were observed with Behavior Mapping method. As exploratory research, the findings of this study provide empirical evidence as a basis for further discussion. It is among the few current studies examining the relationships between architectural environment and the unstructured behaviors of people with dementia. It provides evidence for the activity-friendly facility design, the development of architectural intervention, and the policy to promote indoor environment in day-care facilities of PWD and the older adults. Although the floor plans of the day-care facilities in this study are different, and their space usages vary from one to another, the analyses proved that they share generic properties of architectural environments governing the behaviors of the care recipients. Based on the findings of the study, several design recommendations are offered for various design stages from floor-plan design phase to interior design phase, which is highly beneficial for architects as well as care administrators.