The ruins of the fort are a reminder of the strategic role played by the archipelago. The red-granite fortress was begun in 1800, when Russia controlled Finland, to defend the entry point to the Gulf of Bothnia. This enormous, unfinished fortress, which could hold thousands of soldiers, fell in 1854, during the Crimean War, to the British and French forces. Two years later the peace treaty was signed and the site was abandoned for good.