Kirkistown Castle is an impressive three-storey tower house, built in 1622 by Roland Savage, a Norman landlord, at the site of a ninth-century round tower. It was occupied until 1731, when it was deserted. It post-dates the Plantation, but is fully in the late medieval tower-house tradition. Parts of the bawn wall survive with three-quarter round flanker towers at the angles. The tower was remodelled in Gothic style in 1800 by a Col. Johnston, and in 1836 some further work was performed by a very young Master Montgomery of Grey Abbey. The building was left, however, with a partial roof and broken windows, and the elements soon returned it to disrepair.
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.