Most traditional Japan castles were built in the second half of the 16th century, when in this feudal country real golden years of castle architecture began. Japanese builders of that period usually used wood for building castles that undoubtedly can be called masterpieces. After regrettable damage of the Meiji period and terrible bombings during World War II, only a few dozen castles left in Japan. Some of them had to be reconstructed with concrete. Himeji Castle is one of the most popular. Because of its sophisticated appearance and white walls it was given a nickname "the White Heron Castle". Matsumoto Castle enjoys as much popularity. It was named otherwise, the Crow Castle, because its walls are black. The biggest Japanese castle that played an important role in Japan's history in the 16th century is in Osaka, located on two high rock platforms surrounded by deep moats as befits a former seat of powerful shoguns. The list of buildings of historical value includes the main tower of Inuyama Castle which has been overlooking a high hill at the Kiso River for over six centuries.