Tower of St . Olav The Tower of St . Olav is the one remaining tower of Vyborg Castle . It is a symbol and an architectural landmark of the city of Vyborg . History . The fortress was conceived by Torkel Knutsson , the Lord High Constable of Sweden , who led in the 1290s a crusade to Karelia , the Third Finnish Crusade , which was actually aimed against the Russian state of Novgorod . He chose the location of the new fortress to command the Bay of Vyborg , which was a trading site already used by locals . From the bay , a river leads inland , ultimately connecting the place to several districts , lakes , and indirectly also to rivers going to Lake Ladoga . 1293 construction . By request of Torkel Knutsson the main fortress tower was constructed in 1293 . According to the Russian military historians the first fortifications consisted of a rectangular donjon type tower and the closed perimeter of a defensive wall , which surrounded the tower . Russian archaeological excavations confirm this fact . The builders constructed the tower from huge boulders , according to traditions of the Italian fortification style then dominant in Europe . The tower was named for a legendary king of Norway , Olaf Sacred , who confirmed Christianity in Scandinavia and was later canonised . The foundation of the tower is made of stone laid without application of a building solution ; the tower walls are composed of stones cemented with use of a strong solution and revetted by boulder s . The tower is rectangular ( size is 15 . 5 х 15 . 6 meters ) , with walls 4 . 5 meters thick . The tower top has a crenelated wall on which a wooden gallery for defenders was erected . The castle cellar was used for storage of supplies and a prison , while the ground floor was used for living space . The new fortress was repeatedly besieged by the armies of the Novgorod Republic , the most serious siege occurring in 1322 . In this siege the most advanced artillery of the age was used : stone fougasse , including possibly the heavy arbalest . As a result of excavation , it has been discovered that wooden structures were once attached to the walls of the stone structure . Researchers have discovered traces burnt down in 14th century of a workshop processing bone and sheet bronze . They cannot , however , conclude with confidence whether or not a foundry works was present . In 1403 Vyborg received the official status of a city . Most likely at the beginning of 15th century the coast was connected with the lock by a bateau bridge named Fortress bridge . Before attaining the royal throne of Sweden , Karl Knutsson ( Bonde ) took residence in Vyborg in 1442 and began strengthening and expanding the castle . He constructed new premises and strengthened the castle with new walls and towers , arranging it on the model of the European cities of that time . The tower of St . Olav received one more circle around it , connecting it with a group of buildings with which it was brought under a single roof in 1442 – 1448 . Constructions of later time . In the middle of 16th century Swedish king Gustav Vaza reconstructed and strengthened a fortress for expansion of borders of the state on the east . In 1525 the German count Johan von Hoya , brother - in - law of Gustav Vaza , became deputy of the castle . Instead of taking actions to strengthen the castle as a military fortress he began to arrange balls and tournaments which demanded considerable expenses . King Gustav sent an army to conquer Vyborg and count Johan von Hoya fled to Lübeck . In 1555 when Gustav Vaza was preparing for his next war with Russia he visited Vyborg and spent some time living in the castle . He noted its shabby condition and mentioned in a letter « those lacks and errors » which he has seen in Finland . The king considered it a priority to carry out an urgent reconstruction of the defensive works both in the castle and in the city . Between 1556 and 1560 building was directed by deputy Klas Kristersson Horn . During this reconstruction Vyborg сastle took the general form that it has retained to this day , but Horn did not have time to finish the defensive works and Tower of St . Olav was finally reconstructed by his son , Eric XIV . In 1561 – 1564 the top part of the quadrangular tower was disassembled , and three floors re - erected in the form of an octangle . The tower was built of brick with a roof covered in lead specially brought from Stockholm . Over an entry gate , by order of the king , were placed the arms « three crowns » ; in the tower were placed artillery of large calibre ; and in a cellar was installed a warehouse for kernels . During the Great Northern War Russian armies under Peter I took all the fortresses of Karelia and Ingria : in 1703 – 1704 – Nyenschantz , Jama , Koporye , Noteburg , and Ivangorod . Vyborg fell on June , 13th 1710 . The Medieval interiors of the castle remained up to the middle of 19th century , but the most part have been destroyed by fire . In 1834 lightning struck a flagstaff of the tower , sparking a fire that burnt down the wooden support beams ; the tower was restored in 1844 . From during celebrations on the occasion of opening of Saimaa Canal fireworks were arranged . These ignited the dome of the tower and from there the fire was thrown down on buildings standing nearby , consuming all of Vyborg Castle in flames . The fire consumed the wooden buildings abutting the Tower of St . Olav , and only the Commandant ' s house and buildings of the Forward courtyard escaped . Tower restoration was undertaken by the engineer corps under Colonel E . Lezedov on the orders of Russian Military Office in 1891 – 1894 . The tower gate was given a granite stoop , and the internal premises were built anew , including the addition of a metal ladder mounted to the top part of the tower leading up to a viewing platform . From May 1 , 1913 through August 6 , 1914 Nikolay Suhomlin supervised engineering and civil work on the fortress . In the 1920s Finnish authorities again repaired the tower and partially opened it to the public , but it remained a military facility . Current state . Following the Second World War the territory on which the tower is built passed under the jurisdiction of Soviet Union . The castle lagged behind as a military facility and after 1964 it was transferred to the Vyborg state museum of local lore . In the castle , work continues on the maintenance and safety of the monument , and now Vyborg Castle is seen as a unique monument of West European military architecture that was shaped by developments from the 13th through 19th centuries . Since 2000 the museum has been known as the State museum « Vyborg Castle » . It is now due for major restoration . Artem Novikov , chairman of the Russian Association of restorers , plans to begin restoration in 2010 – 2012 .