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:
Sirmione castle was built near the end of the 12th century as part of a defensive network surrounding Verona. The castle was maintained and extended first as part of the Veronese protection against their rivals in Milan and later under the control of the Venetian inland empire. The massive fortress is totally surrounded by water and has an inner porch which houses a Roman and Medieval lapidary. From the drawbridge, a staircase leads to the walkways above the walls, providing a marvellous view of the harbour that once sheltered the Scaliger fleet. The doors were fitted with a variety of locking systems, including a drawbridge for horses, carriages and pedestrians, a metal grate and, more recently, double hinged doors. Venice conquered Sirmione in 1405, immediately adopting provisions to render the fortress even more secure, fortifying its outer walls and widening the harbour.
Thanks to its strategical geographical location as a border outpost, Sirmione became a crucial defence and control garrison for the ruling nobles, retaining this function until the 16th century, when its role was taken up by Peschiera del Garda.