Älvsborg, also Elfsborg Fortress, is a sea fortress situated on the mouth of the Göta Älv river. It served to protect Sweden's access to the Atlantic Ocean and the nearby settlement of today's Gothenburg and its four predecessors. The fortress was relocated in the 17th century, this New Älvsborg Fortress is still maintained. Of the Old Älvsborg Fortress, only few ruins are visible today in the vicinity of the Carnegie-pier. The new fortress was founded in 1621 by Gustavus Adolphus of Sweden.
In 1643, a settlement in New Sweden, North America, was named Fort Nya Elfsborg, after the Swedish fortress. This settlement was however abandoned in 1655.
References:Visby Cathedral (also known as St. Mary’s Church) is the only survived medieval church in Visby. It was originally built for German merchants and inaugurated in 1225. Around the year 1350 the church was enlarged and converted into a basilica. The two-storey magazine was also added then above the nave as a warehouse for merchants.
Following the Reformation, the church was transformed into a parish church for the town of Visby. All other churches were abandoned. Shortly after the Reformation, in 1572, Gotland was made into its own Diocese, and the church designated its cathedral.
There is not much left of the original interior. The font is made of local red marble in the 13th century. The pulpit was made in Lübeck in 1684. There are 400 graves under the church floor.