First built in 1580, Koriyama Castle was home to Junkei Tsutsui, a feudal lord who overcame many rising local samurais and united Yamato province. In 1585, Koriyama domain (and the castle) was succeeded by Hidenaga Toyotomi, a little brother of Hideyoshi Toyotomi (one of the three greatest Sengoku Period commanders), who made Koriyama a even more prosperous town. Like many other castles, those were the glorious days. Koriyama castle was destroyed during the Meiji Period and part of it was restored in 1980.
Today, Koriyama castle is a popular ruin and a park for the locals. If you want to avoid the regular tour group places for cherry blossom in Nara, the ruins of Koriyama Castle is a good option.