Tenshu (天守) – Main Keep – National Treasure
The three-storey tenshu (天守), or main keep, is the most prominent structure at Hikone Castle and one of only twelve original castle keeps surviving in Japan. Constructed in the early seventeenth century during the establishment of the castle by the Ii clan (井伊氏), it was built using materials transferred from several older castles, including Ōtsu Castle (大津城).
Although relatively small compared with the keeps of Himeji or Matsumoto, the Hikone tenshu is admired for its elegant appearance and sophisticated design. The structure combines elements from different architectural styles, including gables (hafu, 破風) and projecting windows (石落とし ishiotoshi), creating a distinctive silhouette. Built atop a high stone foundation, it commanded extensive views over Lake Biwa and the surrounding castle town.
The keep was designated a National Treasure in 1952 and remains one of the finest surviving examples of early Edo-period castle architecture.
