Japanese castle architecture, Honmaru

Although not always visible today, the Japanese castles were originally surrounded by defense walls, very much like the European castles. However, today only gates or parts of the inner walls are still visible, very few castles still featuring a second or a third row. The innermost area, called honmaru, includes the main tower (tenshu), storehouses and the living quarters for the daimiyo.

Here's a photo taken from the main tower of the Tsuruga-jo from Aizu-Wakamatsu, showing parts of the inner wall, the gate and one yagura tower.