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.References:
Easter Aquhorthies stone circle, located near Inverurie, is one of the best-preserved examples of a recumbent stone circle, and one of the few that still have their full complement of stones. It consists of a ring of nine stones, eight of which are grey granite and one red jasper. Two more grey granite stones flank a recumbent of red granite flecked with crystals and lines of quartz. The circle is particularly notable for its builders' use of polychromy in the stones, with the reddish ones situated on the SSW side and the grey ones opposite.
The placename Aquhorthies derives from a Scottish Gaelic word meaning 'field of prayer', and may indicate a 'long continuity of sanctity' between the Stone or Bronze Age circle builders and their much later Gaelic successors millennia later. The circle's surroundings were landscaped in the late 19th century, and it sits within a small fenced and walled enclosure. A stone dyke, known as a roundel, was built around the circle some time between 1847 and 1866–7.