Fourteen National Treasures of Japan are residential structures from the 15th-century feudal Muromachi period to the early modern 17th-century Edo period. The term National Treasure has been used in Japan to denote cultural properties since 1897. The definition and the criteria have changed since the inception of the term. The residential structures adhere to the current definition, and were designated National Treasures when the Law for the Protection of Cultural Properties was implemented on June 9, 1951. The structures listed include teahouses, shoin (the Ninomaru Palace pictured), guest or reception halls and other rooms which are part of Japanese domestic architecture. While most of the structures are located in temples, one is a castle. In 2009, the early 20th century Akasaka Palace was designated as a National Treasure in the category of "modern residences" (Meiji period and later). It is the only National Treasure in this category. (Full list...)