Japanese castle architecture, Ishi-otoshi

Although designed for military purposes, the Japanese castles were also architectural jewels, carefully designed to combine the defensive ability with esthetically pleasing ornaments. One beautiful example is the fan sloping wall of the Nagoya Castle, which besides its elegance, improves the wall's resistance and to makes it harder to climb.

In other cases, the defensive elements were carefully integrated with the castle's design, so that they now look purely ornamental. One example is the Ishi-otoshi, the Japanese version of machicolation, narrow windows through which the defenders were throwing stones and boiling oil over the attackers. In this photo from Osaka Castle, at the first floor, in the corners and between the windows you can see these sloped portions of the wall, with downward openings. Looking like architectural decorations, it is now hard to imagine their real purpose...