Bočac Fortress is located on the left bank of the Vrbas River, on the half of motorway E661, between Banja Luka and Jajce. It was built in the early 15th century on a rock, in order to defend the crossing over the Vrbas River. The Fortress was mentioned for the first time in a charter from 1448. From 1463 to 1527, when it fell under the Ottoman rule, the city used to be the fortification of the Banovina of Jajce. In the early eighteenth century, Bočac was mentioned as a settlement with a few cannons. It was abandoned before 1833. During the Ottoman occupation it was subsequently fortified and maintained and the fortified walls and towers that surround the large garden of the town are relatively well preserved today.
References:Carlsten is a stone fortress built on the orders of King Carl X of Sweden following the Treaty of Roskilde, 1658 to protect the newly acquired province of Bohuslän from hostile attacks. 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 labour, until 1860 when it was reported finished. The fortress was decommissioned as a permanent defense installation in 1882, but remained in military use until the early 1990s.
The fortress was attacked and sieged twice falling into enemy hands. In 1677 it was conquered by Ulrik Frederick Gyldenløve, the Danish military commander in Norway and in 1719 by the Norwegian Vice-Admiral Tordenskjold. At both occasions the fortress was returned to Swedish control through negotiations and treaties.