The Sejong Government Complex rooftop garden is the world's largest rooftop garden, with a total length of approximately 3.6km connecting 15 government buildings and an area of ​​79,194㎡, the size of 11 soccer fields combined. In order to realize the 'flat city, communicative city, and eco-friendly city' aimed at in the central administrative town master plan that served as the basis for the construction of the Sejong Government Complex, a rooftop with an open view and a horizontal structure was created by breaking away from the vertical structure. It was designed with the concept of 'pure castle play', which involves walking around the castle walls and looking around the inside and outside of the castle.

The rooftop garden was planted with 1,080,000 plants of 187 species, herb garden, medicinal garden, fruit tree and berry garden, There are themed spaces such as vine tunnels, and seasonal tree species are planted so you can see different scenery throughout the four seasons. In addition, an observatory with a panoramic view of the Guinness World Records monument, Sejong Lake Park, and the Presidential Archives, and a large Taegeukgi made of Rose of Sharon were installed to allow visitors to view various landscapes. In addition, by filling the rooftop of Sejong City Hall with about 1㎡ of soil to create a landscaping area, energy loss is blocked, resulting in a savings of 1.4 billion won in heating and cooling energy costs per year.