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:Trenčín Castle is relatively large renovated castle, towering on a steep limestone cliff directly above the city of Trenčín. It is a dominant feature not only of Trenčín, but also of the entire Považie region. The castle is a national monument.
History of the castle cliff dates back to the Roman Empire, what is proved by the inscription on the castle cliff proclaiming the victory of Roman legion against Germans in the year 179.
Today’s castle was probably built on the hill-fort. The first proven building on the hill was the Great Moravian rotunda from the 9th century and later there was a stone residential tower, which served to protect the Kingdom of Hungary and the western border. In the late 13th century the castle became a property of Palatine Matúš Csák, who became Mr. of Váh and Tatras.
Matúš Csák of Trenčín built a tower, still known as Matthew’s, which is a dominant determinant of the whole building.