are 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. Castles in Japan were built to guard important or strategic sites, such as ports, river crossings, or crossroads, and almost always incorporated the landscape into their defenses. Though they were built to last and used more stone in their construction than most Japanese buildings, castles were still constructed primarily of wood, and many were destroyed over the years. This was especially true during the Sengoku period (1467–1603), when many of these castles were first built. However, many were rebuilt, either later in the Sengoku period, in the Edo period (1603–1867) that followed, or more recently, as national heritage sites or museums. Today there are more than one hundred castles extant, or partially extant, in Japan; it is estimated that once there were five thousand. Some castles, such as the ones at Matsue and Kōchi, both built in 1611, remain extant in their original forms, not having suffered any damage from sieges or other threats. Hiroshima Castle, on the opposite end of the spectrum, was destroyed in the atomic bombing, and was rebuilt in 1958 as a museum. The character for castle, '城', by itself read as shiro (its kun'yomi), is read as jō (the Chinese-derived on'yomi) when attached to a word, such as in the name of a particular castle. Thus, for example, Osaka Castle is called Ōsaka-jō (大阪城) in Japanese. Japanese castle is included in Unicode as U+1F3EF 🏯 History Originally conceived as fortresses for military defense, Japanese castles were placed in strategic locations, typically along trade routes, roads, and rivers. Though castles continued to be built with these considerations, for centuries, fortresses were also built as centres of governance. By the Sengoku period, they had come to serve as the homes of daimyōs (feudal lords), to impress and to intimidate rivals not only with their defences but also with their sizes, architecture, and elegant interiors. In 1576, Oda Nobunaga was among the first to build one of these palace-like castles: Azuchi Castle was Japan's first castle to have a tower keep (天守閣, tenshukaku), and it inspired both Toyotomi Hideyoshi's Osaka Castle and Tokugawa Ieyasu's Edo Castle. Azuchi served as the governing center of Oda's territories, and as his lavish home, but it was also very keenly and strategically placed. A short