The paper examines six commercial strips within the large apartment complex built in Seoul from the early 1970s to the early 1980s. Three main research questions are raised. First, what are the urban context, and the regulatory and institutional background of the emergence of strips? Second, how are the strips related to the adjacent streets, and what are their vertical and horizontal architectural profiles? Third, how do the functional programs of the strips affect street environments? The paper discovers the followings. First, the six strips are classified into the introvert, the extrovert, and the intermediate type depending on their spatial relationships with streets and apartment complex. Second, the residential and commercial spaces are either vertically stacked or horizontally separated in architectural and morphological terms. The latter type is an outcome of the verticalization of apartment building. Third, as the strip has continually changed for the last 30 years, some slowly transforms into a part of regional commercial center, whereas some still help to make liveable street. The paper argues that the commercial strip have played an intermediate and buffer zone between the residential and the street, and the private and public; and thus it needs continuous research and discussions from urban and architectural perspectives.