Korean traditional architecture is characterized by its harmony with nature. Ancient architects adopted the bracket system characterized by thatched roofs and heated floors called ondol. People of the upper classes built bigger houses with elegantly curved tiled roofs with lifting eaves. Traditional architecture can be seen in the palaces and temples, preserved old houses called hanok, and special sites like Hahoe Folk Village, Yangdong Village of Gyeongju and Korean Folk Village. Traditional architecture may also be seen at the nine UNESCO World Heritage Sites in South Korea. Bulguksa, a UNESCO World Heritage Site
Western architecture was first introduced to Korea at the end of the 19th century. Churches, offices for foreign legislation, schools and university buildings were built in new styles. With the annexation of Korea by Japan in 1910 the colonial regime intervened in Korea's architectural heritage, and Japanese-style modern architecture was imposed. The anti-Japanese sentiment, and the Korean War, led to the destruction of most buildings constructed during that time.
Korean architecture entered a new phase of development during the post-Korean War reconstruction, incorporating modern architectural trends and styles. Stimulated by the economic growth in the 1970s and 1980s, active redevelopment saw new horizons in architectural design. In the aftermath of the 1988 Seoul Olympics, South Korea has witnessed a wide variation of styles in its architectural landscape due, in large part, to the opening up of the market to foreign architects. Contemporary architectural efforts have been constantly trying to balance the traditional philosophy of "harmony with nature" and the fast-paced urbanization that the country has been going through in recent years