Shot at East Park in Imperial Palace, Tokyo.
In the back of the former main tower of the castle, there is a small gate called 'KITAHANEBASHI-MON'. Although it is located just near the important architecture, the gate is modest. Perhaps, it was built with an intention not to be attacked from this direction.
It is built on the top of the drop-off in fact. Besides, the bridge built just outside of this gate was a drawbridge. If the bridge were lifted, it could be difficult to enter into the castle from the gate. However, the imperial palace, which was the former Edo castle, has never been attacked.