Kamiyama Castle (Kamiyama-jyo) was beautiful with the surrounding sakura in blossom.
It is a classic example of Edo period castle architecture. According to the pamphlet we were given at 上山温泉下大湯 -- the public hot spring where we bathed -- this castle was built in the year Showa 57.
(For any non-Japanese readers who might not be familiar with the Japanese calendar, Showa 57 equals ... 1982.)