"요새" (yosae) refers to a type of fortification or defensive structure used in ancient Korea. These structures were typically built on elevated ground, providing a strategic advantage for surveillance and protection against invasions. They often featured walls made of stone or earth and were used by military forces to defend territories. In modern times, "요새" can also refer to historical sites that attract tourists and serve as reminders of Korea's rich history. Many of these sites, such as the Namsan Fortress in Seoul, offer visitors a glimpse into the architectural and military practices of the past.