In the beginning of the 14th century a peace treaty was made between Sweden and Novgorod (Russia), according to which the eastern border of Sweden went through Savonlinna region. At that time Finland was a part of Sweden. However, the border line remained unfixed and this caused continual fights. In the 15th century Grand Duchy of Moscow became more powerful and even more threatening.

There was only one castle in Wyborg, further down in south-east, to protect the eastern border of Sweden-Finland. The Swedes decided to build a castle in order to improve safety on the eastern border and to control an important waterway. Olavinlinna castle was founded by Erik Axelsson Tott. The building work began in 1475. The Russians did their best to disturb the work, in their opinion the castle was built on their side of the border.

Erik Axelsson was a Danish knight (in the 15th century Sweden-Finland was still united with Denmark and Norway). He named Olavinlinna Castle, or St. Olof's Castle, after the patron saint of all knights, St. Olof. St. Olof lived in the 11th century and he was a famous Norwegian crusader.

Olavinlinna castle was built on a rocky island in Lake Saimaa area. The castle was easy to defend all year round, water floats around the castle so fast that it hardly ever freezes. The medieval castle consisted of three towers and the connecting walls between them. Two of these towers still exist, the Bell Tower and the Church Tower. The third, St.Eric's Tower, tumbled down or was pulled down in the beginning of the 18th century. Later a bailey, two more towers and apartments were added.

Olavinlinna castle served as a Swedish border castle until the beginning of the 18th century. The Great Northern War broke out in 1700. In 1714 Olavinlinna Castle had to surrender to Russian soldiers, there was no food and munition left in the castle after a long siege. The first Russian period was short and was over in 1721. In a peace treaty the border line was moved again and Swedes got their castle back.

In 1743 Olavinlinna Castle became a Russian garrison again after a peace treaty of Turku. At that time Russians stayed in the castle for nearly 100 years.

Olavinlinna Castle lost its' military purpose in 1809 when Finland became an autonomous part of Russia. However, Russian soldiers stayed in the castle until 1847. Finland became independent in 1917.

In the 1850's castle served as a prison for a few years. In the 1860's two fires caused extensive damage to the castle. First restorations were made already in the 19th century, but the castle was restored thoroughly between 1961-1975.

Olavinlinna Castle is nowadays run and owned by the Finnish state. It is one of the best preserved medieval castles in Nordic countries. It hosts Savonlinna Opera Festival every July ( http://www.operafestival.fi/ ). The castle is open to tourists all year round and it is a popular venue for e.g. wedding receptions, concerts and theatre performances.