I think it’s seriously time I visit Marugame Castle again. It is one of the few (12 I think) remaining castles in Japan that hasn’t been rebuilt (in other terms, the main tower is the original from the Edo Period). It is also said to be the smallest castle with the largest walls. I don’t know if this is true, but the main tower is clearly small, and the stone walls are clearly huge.
To help you wait until I return there, I invite you to read about my first visit there during my first trip to Japan.