고구려의 국토를 가장 많이 넓힌 왕은 누구인가?
Goguryeo experienced a golden age under Gwanggaeto the Great and his son Jangsu. During this period, Goguryeo territories included three fourths of the Korean Peninsula, including what is now Seoul, almost all of Manchuria, parts of Inner Mongolia, and parts of Russia. There is archaeological evidence that Goguryeo's maximum extent lay even further west in present-day Mongolia, based on discoveries of Goguryeo fortress ruins in Mongolia.
Gwanggaeto the Great and his son Jangsu