The Kajaani castle was built on the Ämmäkoski island of the Kajaani river in the centre of Kajaani, Finland, in the 17th century. It functioned as a governing centre, a prison, and a refuge for residents during times of persecution. 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. Construction of the Kajaani castle began in 1604 and was completed in 1619. At first the castle only consisted of a stone wall, two round towers, and wooden buildings in the yard inside the castle. The second phase of construction was ordered by Count Peter Brahe which began in the 1650s and was completed in 1666. Upon completion many of the original wooden structures had been replaced with stone and the castle had become a fortress. During the “Greater Wrath”, Russian forces kept the castle under siege for months, and upon its surrender they blew up much of the fortress, transporting the inhabitants to Russia to be imprisoned. Kajaani Castle is thought to be the smallest stone castle, and the most northernmost, in the world. https://www.discoveringfinland.com/destination/kajaani-castle/

The building of Olavinlinna Castle began in 1475. The Danish-born founder of the castle, knight Erik Axelsson Tott, decided that a powerful fortification should be build to protect the strategically important Savo region http://visitsavonlinna.fi/en/products/statue-musta-paessi-black-ram/

The Fortress of Lappeenranta is a unique place in South-Eastern Finland. Inhabited and full of life even today, it once formed part of a defence system that also included the fortress of Suomenlinna in Helsinki and the fortress of Hamina. Although different in size, all three of these fortresses are of a similar nature and share the same passion for development. While seeking to protect and preserve these areas through careful land use planning, they also aim to increase services and levels of activity around the year. The Fortress of Lappeenranta was constructed as a border fortress, forming part of the chain of fortresses between Finland and North-Western Russia. Over the centuries, the Fortress was alternately held by the Swedes and Russians. Today, the Fortress of Lappeenranta is a valuable component of Finnish, Russian and Swedish cultural heritage and forms part of the Castles and Fortifications chain of cultural destinations. http://www.discoveringfinland.com/destination/the-fortress-of-lappeenranta/

Forum Marinum, a National Specialist Museum for Finnish maritime and naval history standing next to Turku Castle, is a nautical experience suitable for all ages. http://www.visitturku.fi/en/forum-marinum-maritime-centre_en