The concept of “full-age” urban public spaces is a critical aspect of modern urbanization, enhancing the multifunctionality of contemporary urban public spaces. This paper examines the design of urban public spaces using “Little Island at Park 55 in New York” as a case study. It delves into three key aspects: spatial intensive utilization, functional agglomeration, and landscape aggregation design. By thoroughly interpreting the original topography of the island space and employing classical Chinese garden techniques, particularly “scenery supporting,” this study analyzes the design evolution and core principles of the case. It summarizes the case’s value and underscores the significance and necessity of all-age inclusive design in modern urban public spaces.