Hamada Castle, which lasted roughly 250 years from 1620, is now only a stone wall, but in spring it is a popular spot for cherry blossom viewing.
The stone steps leading up to where the castle keep stood are so large that you can walk up them and think about how people in the Edo period must have carried them. When you reach the top, you can also see Sotonoura, a Japanese Heritage Site, and the view may be the same view of the people of the past.