During the Viking Age, Birka was an important trading center. The archaeological sites of Birka and Hovgården, on the neighbouring island of Adelsö, make up an archaeological complex which illustrates the elaborate trading networks of Viking Scandinavia and their influence on the subsequent history of Europe. Generally regarded as Sweden's oldest town, Birka (along with Hovgården) has been a UNESCO World Heritage Site since 1993.
Established in the middle of the 8th century and thus being one of the earliest urban settlements in Scandinavia, Birka was the Baltic link in the river and portage route through Ladoga and Novgorod to the Byzantine Empire and the Abbasid Califate. Birka was also important as the site of the first known Christian congregation in Sweden, founded in 831 by Saint Ansgar.
Sources are mainly archeological remains. No texts survive from this area, though the written text Vita Ansgari ("The life of Ansgar") by Rimbert (archbishop of Bremen-Hamburg, c. 865) describes the missionary work of Ansgar around 830 at Birka, and Gesta Hammaburgensis Ecclesiae Pontificum (Deeds of Bishops of the Hamburg Church) by Adam of Bremen in 1075 describes the archbishop Unni, who died at Birka in 936. St Ansgar's work was the first attempt to convert the inhabitants from the Norse religion to Christianity, and it was unsuccessful.
Both publications are silent on Birca's size, layout and appearance. Based on Rimbert's account, Birca was significant because it had a port and it was the place for the regional ting. Adam only mentions the port, but otherwise Birca seems to have been significant to him because it had been the bridgehead of Ansgar's Christian mission and because archbishop Unni had been buried there.
Birka was abandoned during the later half of the 10th century. Based on the coin finds, the city seems to have silenced around 960. Roughly around the same time, the near-by settlement of Sigtuna supplanted Birka as the main trading centre in the Mälaren area. The reasons for Birka's decline are disputed. A contributing factor may have been the post-glacial rebound, which lowered the water level of Mälaren changing it from an arm of the sea into a lake and cut Birka off from the nearest (southern) access to the Baltic Sea. The Baltic island of Gotland was also in a better strategic position for Russian-Byzantine trade, and was gaining eminence as a mercantile stronghold. Historian Neil Kent has speculated that the area may have been the victim of an enemy assault.
In search of Birka, National Antiquarian Johan Hadorph was the first to attempt excavations on Björkö in the late 17th century. The later excavations soon indicated that a major settlement had been located on the island and eventually. Ownership of Björkö is today mainly in private hands, and used for farming. The settlement site, however is an archaeological site, and a museum has been built nearby for exhibition of finds, models and reconstructions. It is a popular site to visit during the summer times.
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.