Just a minute away from the castle Olavinlinna in Savonlinna you can visit a small boat museum. I recommend it to you. In the exhibition hall you can learn about the history of Savonlinna aswell as various aspects of maritime. In the outside exhibition you can enter some boats and look at their interior.
A must in Finland is the visit to the different ‘Linnas’, heavily fortified castles. Most famous upon them are the Soumenlinna on an island just off Helsinki and the Olavinlinna in the town Savonlinna. Here in Savonlinna I already came twice, one time in winter and one time in summer. It was one of the sights I could visit on my my drive back home to Germany after a year in Finland. That time my visit was in February and the landscape was covered by ice and snow. Coming back here in summer was therefore a very interesting experience.
Olavinlinna (the fortification of Olavi) dates back to 1475 when it was founded. Its name derives from the holy Olavi. I recommend you to take part in a guided tour. Additional to the castle you can visit the boat museum which is two minutes away. As I remember you can get ticket for that also at the entrance to the castle. I will show you some of the pics I took in and of the castle.