Kajaanin Linna, as the finns say, is nowadays just a ruin; but once it was a fine, strong and fearful castle at 64° 13' N, in the remote wilderness of north Finland, not far from the the arctic circle.
By 1666 the castle, although not a perfect fortification, presented a formidable obstacle to any invasion from the east. Kajaneborg, as the castle was known in Swedish, took the form of a long rectangle with a circular tower at each end.
Its purpose was to protect Northern Ostrobothnia from Russians and oversee movements on the inland waterway. It also functioned as an administrative centre and a prison.
It was so formidable that throughout the 1600s the Russians did not even attempt an attack. Only during the Great Northern War and after a long siege did the castle fall to Russian forces. On taking the castle the Russians proceeded to blow it up in March of 1716.