Christiansfjel Fortress was initially established by Count Wedel-Jarlsberg in 1683 as Hammersberg Skanse. A tower with a cellar powder magazine was among the first buildings at this Norwegian fortress. During Christian V's 1685 visit to Norway he visited Hammersberg skanse on June 14th. Recognizing its important location on the Swedish border, he renamed the fortress Christiansfjell and directed continued improvements. An extensive report of the visit includes illustrations of the fortress at that time.
After the Great Northern War some of the smaller border forts were determined to be more expensive than their utility justified and they were closed. On July 13, 1742 Christiansfjell Fortress was closed and the materials were moved to Kongsvinger Fortress.
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.