The site of Marstrand was chosen because of its location and its access to an ice free port. Initially a square stone tower was constructed, but by 1680 it was reconstructed and replaced by a round shaped tower. Successive additions to the fortress were carried out, by the inmates sentenced to hard labor, until 1860 when it was reported finished. Carlsten was exclusively a prison form men: Metta Fock was in 1806-1809 the only female prisoner to have been kept here. The fortress was decommissioned as a permanent defense installation in 1882, but remained in military use until the early 1990s.