These were constructed along the ridges of Mt. Pibongsan in Maesan-ri about 17 kilometers northeast from Ansung City. Presently, only the 2.5 meter high stone fortifications remain. Larches and young pines form a forest within the walls, and paddy fields are scattered to the south of the valley. The fragments of building stone and the platform rock for the commander are scattered around a spot which is assumed to have been the east gate. A gate, presumed to be the south gate, still stands due south. Four cornerstones and fragments of roof tiles are scattered around the site, which might have been the platform for the commander. A shrine is found within the walls. It is a monument to General Song Munju for courageous deeds during the invasion of the Mongol army. When the general was defending Chukchusansong Fortress in the 23rd year of King Kojong's rule of the Koryo Kingdom, the Mongol army approached the fortress and tried to persuade him to surrender. Instead, he charged out of the fortress and dislodged the enemy from the hill. As the Mongol army attacked again with guns, destroying the four gates, he struck back with guns from inside the fortress. The enemy attempted various attacks for fifteen days, but couldn’t take the fortress. Eventually, they burnt the equipment for the siege operation and withdrew. The general received a promotion for his deeds