The aging of the population and the increase in single-person households has led to lower economic status among older persons in Seoul, which will likely continue to decline in the future. Making Seoul an age-ready city will require additional attention to many such facets of life where older persons, especially those living in single-person households, are concentrated. This case study focuses on the built environment in terms of three domains: aging in place, spatial accessibility and mobility, and social inclusion. Aging in place allows older persons to remain in familiar homes and surroundings. Spatial accessibility and mobility allow them access to destinations and facilitate getting around by providing age-friendly modes of transportation and making the urban environment barrier-free. A livable life also requires social inclusion instead of isolation. Older persons should be able to have connections with all generations of people.