In general, each kuruwa of a mountain castle was so small that only limited facilities could be installed, but each kuruwa was large in a hira-jiro (castle built on the level ground) so that large facilities, such as a palace, could be built there.
一般に山城では各曲輪の面積が狭く設置可能な施設は限られていたが、平城では各曲輪の面積が広く御殿など大規模な施設の設置が可能であった。