South Korea, my adopted home for almost two years, has about 50 million residents as of the last census, in 2015. Most of them are settled in the country's urban areas. About 22 million residents, for example, live in Seoul, the capital in the country's northwest corner, and its adjacent province, Gyeonggi.

As an experiment to create a choropleth map with D3 and NPR's dailygraphics rig, which drives most of the visualizations here, I've mapped the total population by municipal districts. In this example, Seoul is outlined with red:

I am, of course, not a citizen of South Korea. I'm a "foreigner" — as we're referred to here. This is where the 1.3 million foreigners — many of them ethnic Koreans who immigrated from China — have settled across the country. Again, Seoul is outlined with red:

And this map shows the roughly 330,000 foreigners living in Seoul proper. This time I've highlighted Yongsan-gu, my home district in the city center: