The Sainte-Gaubuge priory was originally a hamlet, which is very well preserved. All the houses are located around the priory. The church building dates from the 13th, 15th and 18th century. The canons of St. Denis are at the origin of the most beautiful architecture sites. Rich carved decorations (13th and 15th century), the house of the prior has magnificent chimneys listed (15th century), and the vaults (13th century) are worth of seeing. Guided tours are available.
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.