Goryōkaku

is a star fort in the Japanese city of Hakodate on the island of Hokkaidō. It was the main fortress of the short-lived Republic of Ezo.
History.
Goryōkaku was designed in 1855 by Takeda Hisaburō. His plan was based on the work of the French architect Vauban. The fort is shaped like a five-pointed star. This allowed for greater numbers of gun emplacements on its walls than a traditional Japanese fortress, and reduced the number of blind spots where a cannon could not fire.
The fort was built by the Tokugawa shogunate to protect the Tsugaru Strait against a possible invasion by the Russian fleet. 
Goryōkaku is famous as the site of the last battle of the Boshin War ("Goryōkaku no Tatakai"). The fighting lasted for a week (June 20-27 1869).