Japanese castles, water moats

Many Japanese castles were originally built with several concentric walls, designed to protect the castle's buildings. To further slow down the enemy troops, elaborate canals were dug around these walls, and in the case of flatland castles, the moats were also filled with water.

In modern times, in many cases the old ditches were covered by the towns growing up around, but there are surviving castles preserving at least the innermost moat (the Matsumoto Castle). Also, some of the reconstructed castles, such as the Odawara Castle, were rebuilt together with the moats, as you can see in this photo...