Castles

"Japanese castles (城 shiro) were fortresses constructed primarily of wood and stone. They evolved from the wooden stockades of earlier centuries and came into their best-known form in the 16th century. …

The earliest known castles date from Yayoi Period (300 BC-300 AD). During the Sengoku Period ( The Warring States Period), as many as 25,000 castles were built. There are five national treasure castles …