Due to terrain. According to Baidu Maps, due to terrain reasons, most of the rivers in South Korea flow into the Yellow Sea and the East China Sea through the western or southern continental slopes, so the roads in South Korea are all slopes. The Republic of Korea, referred to as "South Korea", is located in the southern part of the Korean Peninsula in East Asia, surrounded by sea on three sides, the Yellow Sea to the west, the Korean Strait to the southeast, the Sea of ??Japan to the east, and adjacent to North Korea across the 38th Parallel Demilitarized Zone to the north.