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.
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 Republic 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.
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 fac