Japanese castle architecture, Hidden Ishi-otoshi

Tenshu, the main donjon of the Japanese castle, was the last place of defense against the attackers, so it was designed to be a hard-to-conquer fortress. But tenshu was at the same time the symbol of the lord's power and wealth, so the aesthetics were very important...

So, to achieve the perfect combination of utility and pleasure, some defense elements were carefully integrated in the castle's aesthetic design. That was the case with the openings for archers (Ya-zama) or the openings used to throw stones and hot oil (Ishi-otoshi) over the attackers.

A good example of such a design is the Osaka Castle and an even more interesting case can be admired at the Matsumoto Castle: here, the Ishi-otoshi openings are almost unnoticeable, perfectly disguised by the black panels surrounding the castle's first floor, right above the walls...