The Kajaani castle (Finnish: Kajaanin linna, Swedish: Kajaneborg, Kajaneborgs slott, or with older spelling Cajanaborg) was built on the Ämmäkoski island of the Kajaani river in the centre of Kajaani, Finland, in the 17th century. Today, only roofless ruins remain of the castle.
The castle functioned as an administrative centre, a prison, and a military strongpoint. The most famous prisoner in the castle was the historian Johannes Messenius, who was forced to live in the poor conditions of the castle from 1616 to 1635.
Count Peter Brahe ordered a second construction stage of the castle, which was started in the 1650s and completed in 1666. During this construction stage, many wooden structures of the castle were replaced with stone structures to form a fortress.
During the Great Northern War (also known as the "Greater Wrath"), Russian forces sieged the castle for several months, until it was finally forced to surrender because of lack of food, firewood and ammunition. Shortly after this, the Russians exploded the castle and its inhabitants were transported to Russia to be imprisoned.
In 1917 a hydro-electric plant was built at Ämmäkoski.
The first wooden bridge on top of the ruins was built in 1845. By 1937 the castle-island became a fundament for a new road-bridge made of concrete.
The bridge called Linnansilta ("castle bridge") was originally the only bridge across the Kajaani river. After the construction of later bridges, the traffic on Linnansilta has reduced and the authorities have drafted plans to take down the bridge and give this national monument a due and proper restoration.
- The Kajaani castle is considered to be the smallest stone-castle in Europe and the northernmost castle in the world.
- The castle figures in the novel The Czar's Spy, by William Le Queux, where it is a terrifying prison held by the Russians who occupy Finland.
- Drawing of Kajaani Castle, made 1732
- Castles and Fortifications in Finland
- Kajaani Castle by the Kainuu Museum
- Kajaani Castle by the City of Kajaani
- Kajaani Castle by the University of Oulu
- The National Board of Antiquities
- Media related to Kajaani Castle at Wikimedia Commons