Here you are on its ruins.
The fort is named after King Gustav III's brother, Duke Karl.
This unimpressive defensive battery consisted of two cannons with a four-pound charge of powder. A small sentry box housed the town's militia in 1809, but it soon disappeared. By 1844, it was reported that there was neither a flagpole nor any other structure.
Today, only a few stones remain, the remains of a powder magazine and paved areas.
Its renovation dates from 2011.