Korean architecture (한국건축) refers to an architectural style that developed over centuries in Korea. Throughout the history of Korea, various kingdoms and royal dynasties have developed a unique style of architecture with influences from Buddhism and Korean Confucianism. Having been deeply influenced by Chinese architecture, traditional Korean architecture can be mostly recognized by its sloping roofs. Just like in the case of other Korean arts, Korean architecture is distinguished by its naturalistic tendencies, simplicity, economy of shape, and avoidance of extremes. In Korean architecture, buildings are structured vertically and horizontally. A construction usually rises from a stone subfoundation to a curved roof covered with tiles, held by a console structure and supported on posts; walls are made of earth (adobe) or are sometimes totally composed of movable wooden doors. Architecture is built according to the kan unit, the distance between two posts (about 3.7 meters), and is designed so that there is always a transitional space between the "inside" and the "outside." The console, or bracket structure, is a specific architectonic element that has been designed in various ways through time. If the simple bracket system was already in use under the Goguryeo kingdom (37 BC – 668 AD)—in palaces in Pyongyang, for instance—a curved version, with brackets placed only on the column heads of the building, was elaborated during the early Goryeo (Koryo) dynasty (918–1392). The Amita Hall of the Buseok temple in Yeongju is a good example. Later on (from the mid-Koryo period to the early Joseon dynasty), a multiple-bracket system, or an inter-columnar-bracket set system, was developed under the ancient Han dynasty in China influence during the Mongolian Yuan dynasty (1279–1368). In this system, the consoles were also placed on the transverse horizontal beams. Seoul's Namdaemun Gate Namdaemun, Korea's first national treasure, is perhaps the most symbolic example of this type of structure.