noun
inner castle; main keep; innermost enclosure
Refers to the central, most fortified area of a Japanese castle, often containing the main keep (天守). Contrasts with 外城 (そとじろ/がいじょう), the outer castle or enclosure.
See also: 外城
内城は城の最も重要な防御拠点だった。
The inner castle was the most important defensive stronghold of the castle.
この城の内城には天守がそびえている。
The main keep towers over the inner enclosure of this castle.