Åland's history is closely bound up with the power struggles of the Baltic. The islands' strategic position — in the middle of the sea lane between Stockholm and St Petersburg — gave them a disproportionately large role in Nordic history.
Kastelholm Castle
Kastelholm Castle was built in the latter half of the 14th century (first mentioned in 1388) and served as one of the Swedish crown's most important fortresses in the Baltic region. It is today well preserved and open for visits during the summer season. Nearby is Jan Karlsgården open-air museum.
Kastelholm is about 25 km northeast of Mariehamn along main road 2.
Bomarsund — Russian fortress and European history
During the 1830s, the Russian Empire began building a massive fortress complex at Bomarsund. It was never completed — during the Crimean War in 1854 a British-French fleet bombarded the complex to ruins in September 1854.
Today, dramatic ruins line the waterfront with information boards explaining the events.