In Finland there happens to be 7 main castles:
Turku Castle: It was built in 1280 i.e. It was destroyed by bombing in 1941, but restored during the next 20 years. Now it is a museum and venue for exhibitions.
Hame Castle: It’s believed to have been built at approximately the same time as the Turku castle. The castle served as a prison at 1837-1972. The castle is now presented as a historical monument.
Viipuri Castle: It isn’t known when the Viipuri castle was built. It is now part of Russia. Viipuri castle wasn’t very important to the Russians, therefore abandoned by them.
Raseborg Castle: It was built in 1374 i.e. It was the seat of a bailiff who was the administrator for the western half of the south coast of Finland. It is now used for tourism.
Kastelholm Castle: It was built in 1384 i.e. Aland was separated from the castle county of Turku and the Aland islanders were reluctantly subjected to a bailiff. Kastelholm castle is preserved as an architectural and historical monument.
Olavinlinna Castle: It was built in 1475. It was the first Finnish castle to be built for use in the era of firearms. It is like most of the castles, a place for tourism, and every year there is an opera festival!
Kuusisto Castle: It was built in 1317. It was unfortunately soon after destroyed in 1528. It is now used as a museum.