Hwaseong Fortress
Construction started near Mount Paldalsan in January 1794. Construction was finished in September 1796.  Chae Jae-gong supervised the building process. Chae Jae-gong was a former minister in the government and the magistrate of Yeongjungchubu County.  Engineers made new tools to help build the fortress.  The Geojunggi was one of these new tools.  It is a traditional Korean crane. They also made potter's wheels were created.  They were used to move and put together large stones for the wall.