Cheolli Jangseong (lit. "Thousand Li Wall") in Korean history usually refers to the 11th century northern defense structure built during the Goryeo dynasty in present-day North Korea, though it also refers to a 7th century network of military garrisons in present-day northeastern China, built by Goguryeo, one of the Three Kingdoms of Korea.
Read more about Cheolli Jangseong: Goguryeo Period, Goryeo Period