Olavinlinna Castle is the stunning 15th-century three-tower castle located in Savonlinna. The Castle is built on an island and it is the northernmost medieval stone fortress in the world. Its most famous event is the Savonlinna Opera Festival held each summer since 1912. Olavinlinna offers a amazing experience for anyone interested in history, culture, art, and design.
You can admire the Castle from the shores, or buy admission to the museum exhibitions inside the castle. If you want to join a guided tour, you can find more information about it from here: https://www.kansallismuseo.fi/en/olavinlinna/guided-tours
Or
In July, go to opera!
https://operafestival.fi/en/