Castle Wild (Wildburg) lies southern behind the Castle Treis. It was built in the 13th or 14th century, probably as protection of the southern side of the castle Treis. In the fifties it was restored and made fit to live in. Back then, the northern situated, almost square, donjon was repaired and received a new roof. The great hall and other outbuildings were also rebuilt. Other buildings and the circular wall are just ruins. Wildburg is private property so you can visit it only from the outside.
References:Goryōkaku (五稜郭) (literally, 'five-point fort') is a star fort in the Japanese city of Hakodate on the island of Hokkaido. The fortress was completed in 1866. It was the main fortress of the short-lived Republic of Ezo.
Goryōkaku was designed in 1855 by Takeda Ayasaburō and Jules Brunet. Their plans was based on the work of the French architect Vauban. The fortress was completed in 1866, two years before the collapse of the Tokugawa Shogunate. It 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 Meiji government.
Goryōkaku is famous as the site of the last battle of the Boshin War.