Takasaki Castle located in Takasaki City, Gunma Pref. was built in 1598 by Ii Naomasa, one of the four powerful retainers of Tokugawa Ieyasu. With the construction of the Nakasendo Road, which connects Edo and Osaka, Ieyasu recognized the strategic importance of Usui Pass (in present-day Annaka City, Gunma Pref.) and ordered Naomasa to build the castle. In 1600, after the Battle of Sekigahara, Ii Naomasa was transferred to Sawayama Castle in Ohmi province (present-day Shiga Pref.), a lot of fudai daimyo such as the Suwa clan, the Sakai clan, and the Matsudaira clan resided in Takasaki Castle by turns till the Meiji Restoration. The castle was turned over to the Meiji government in the 1871 due to the abolition of the han system. The castle ruin was once used as a military station for foot soldiers but now it has been arranged into Takasaki Castle Ruin Park, where citizens visit for recreation and relaxation, and enjoy 3,000 Somei Yoshino cherry trees bloom in spring.