Treasure No. 1710 (designated on March 3, 2011)Gongsimdon is an elevated watchtower mounted on a section of a fortress wall to observe and fire upon an approaching enemy. Constructed on March 10, 1796, in the 20th year of King Jeongjo’s reign, the tower has a three-tiered structure whose lower side (the bastion) was built with stones and whose upper side with bricks. Its interior is fitted with stairs and a combat facility. It is said that on his visit to the fortress in January 1797, the 21st year of his reign, King Jeongjo expressed satisfaction over its being “the first defense structure of its kind in the country.” The structure was designated as a treasure in recognition of its historical, academic and architectural value as a building displaying both a creative architectural style and an effective use of materials.