 The walls were mostly complete in 1830, and after comprehensive visits to other fortresses in Europe, fortress architect Johan av Klen presented plans similar in style to the Fort Winiary in Posen (present-day Poznań).Due to its great expense and reduced funding, the fortress wasn't in operation until 1870, and wasn't fully completed until 1909.To compensate for the rapidly evolving technology of artillery during this time, Vaberget Fortress was built in the early 1900s five kilometers west of Karlsborg to provide additional protection to the main fortress.