It is believed that Odawara Castle was first built in the middle of the 15th century when Mr. Omori entered the Odawara region. After becoming the residence of the Sengoku daimyo Odawara Hojo around 1500, it was gradually expanded and maintained as a central base for Kanto rule, and the scale of the castle was maximized when the entire structure surrounding the castle was completed in preparation for Toyotomi Hideyoshi's invasion. It reached and developed into the largest medieval castle in Japan. In the Edo period, Odawara Castle became under the control of Ieyasu Tokugawa, and with his vassal Okubo as the lord of the castle, the scale of the castle was reduced to within Sannomaru. After Mr. Inaba became the owner of the castle, large-scale renovation work began, and it was reborn as a modern castle. After that, Mr. Okubo became the lord of the castle again, and played an important role until the end of the Tokugawa shogunate as a key point for the defense of the Kanto region ahead of Hakone and as the residence of the Fudai Daimyo who supported the Bakuhan system. However, Odawara Castle was abandoned in 1923, most of the buildings were demolished, and all the remaining stone walls collapsed due to the Great Kanto Earthquake of 1923. Most of the current Odawara Castle Ruins and part of the entire structure of Honmaru and Ninomaru are designated as national historic sites. In addition, it was developed as a "castle park" centered on the main enclosure, and the castle tower was reconstructed in 1960, followed by Tokiwa Kimon in 1971, Copper Gate in 1997, and 2009. In the year (2009), the horse gate was restored. Furthermore, in Odawara City, we are working on full-scale historic site maintenance with the aim of making the Odawara Castle Ruins, which is a valuable cultural heritage, even more familiar and passing it on to future generations.