South Korea is rapidly becoming a multiethnic society with over one million foreign residents as of September 2007, which is a significant social phenomenon given South Korea's long history of "mono-ethnic" ideology and its non-immigrant political system. This research is a preliminary study of South Korea's changing ethnic landscape with an examination of Seoul's growing foreign communities. This study utilizes a qualitative research method with its analytical framework developed from the following three groups of studies: 1) development of large metropolis with the advent of globalization involving massive flows of labor and capital, 2) ethnic residential enclaves in immigrant societies; and 3) South Korea's foreign residents and discourse on multiculturalism. This study reveals that Seoul has two different types of foreign communities: 1) foreign residential communities formed around schools since the 1970s, which are represented by the Japanese and Chinese communities, respectively; and 2) "foreign cultural communities," non-permanent but regularly forming one. Both of these communities are found as important space for long-term foreign residents living in a nation with a 98% ethnic majority population. This study suggests that we need to develop a new sociological perspective in understanding foreign communities in non-immigrant societies such as South Korea in the age of globalization.