Foundation of Sumpu Castle’s Main Tower
The foundation of Sumpu Castle’s keep, or tenshu, is the largest ever built in Japan. The keep burned down in 1635 and was never rebuilt. An ongoing archaeological study has revealed that part of the foundation is still intact. The site is open to the public, offering a rare chance to see some of the construction methods used to build stone fortifications in the sixteenth and seventeenth centuries.
Tokugawa Ieyasu (1542–1616) lived in Sumpu (now the city of Shizuoka) in his youth. In the late 1580s he took control of Sumpu province and built Sumpu Castle. Ieyasu would later unify Japan under his control after his decisive victory at the Battle of Sekigahara (1600). He became shogun in 1603 but passed control to his son two years later and retired to Sumpu. In 1607, he embarked on an ambitious expansion of the castle. Daimyo from all over Japan were ordered to contribute to the project—many sent workers to dig moats and build walls. The workers engraved the crests of their domains and other symbols on some of the stones, many of which are still visible today.
Ieyasu’s new tenshu was rebuilt on the same site as the previous one, but on a much grander scale. The archaeological dig has uncovered the foundations of both the older and newer keeps, as well as that of a moat built before Ieyasu’s time. The way stone walls were constructed developed over time, and these changes can be seen in the different foundations. The stones of the earlier structures are uncut, and the walls have a gentle slope. The stones used for Ieyasu’s grand keep were cut to fit snugly, and the walls are much steeper.
After the 1635 fire, most of the castle’s reconstruction was finished by 1638, but the tenshu keep was never rebuilt. After the end of the Tokugawa shogunate in 1867, Sumpu Castle became the property of the newly established Empire of Japan. In 1896, the castle grounds were given to the Army and were used by the 34th Infantry Regiment. The top of the tenshu foundation was demolished and used to fill in the innermost moat, creating a flat field to build barracks and other military buildings. In 1949, the city of Shizuoka purchased the site and transformed the grounds into a public park. Excavation of the foundation of the tenshu began in 2016.
