Most civilizations develop near water, as it is a source of life. Crops need it to grow. Merchants need it to transport their goods. People need to drink it to survive. However, while in the past, living near the water was a good thing, it can present a problem in modern times.
In the United States, we expanded into the Great Plains as the population grew and people moved West. But the Koreans didn't do that; they couldn't because of the hard granite mountains that exist everywhere in their country. Instead, they built their homes around the mountains where the river valleys lie. The Han River ran naturally through these valleys. When the population was smaller, this worked. But as soon as more people started living here, they ran into an issue: there was a lack of space for them to build apartments in these relatively small valley areas
