The Kitahanebashi-mon Gate is now one of entrances of
the Imperial Palace East Garden opened to the public.
That was the nearest gate to the Tenshukaku Donjon and the main building house of the old Edo Castle.
The moats in this area are so deep and the stone walls are so high, because the security against invaders was very tight in the Edo period.
You can walk and run around the Imperial Palace on the sidewalk enjoying seeing richness of green and water in the center of Tokyo.
In such a rainy season in June to July, "hydrangea blooms" are vivid in your eyes.