Kajaani Castle: A 17th-Century Swedish Fortress in Finland

Visitor Information

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Popularity: Medium

Official Website: www.luontoon.fi

Country: Finland

Civilization: Early Modern

Site type: Military

Remains: Castle

History

Kajaani Castle, located in the town of Kajaani in Finland, was constructed by the Swedish Empire in the early 17th century. The castle was established following Sweden’s acquisition of the Kainuu region through the Treaty of Teusina in 1595 and was built to secure Sweden’s northern borders against Russian incursions.

Construction began in 1605 on a small island in the Kajaani River, positioned strategically between two rapids to control river traffic and protect the area. Work progressed slowly due to limited labor and materials, with local peasants conscripted to assist for a few days annually. Initial leadership came from master builder Isak Rasmusson until 1615, after which journeyman Lars Thomasson oversaw the project. By 1619, although the castle remained incomplete, it was functional enough to serve as a prison and administrative center. During this time notable prisoners included historian Johannes Messenius, who spent nearly two decades imprisoned and authored a significant historical work, and the poet Lars Wivallius.

In the mid-17th century, Count Per Brahe the Younger, appointed as the castle’s fiefholder, initiated major renovations. He founded the town of Kajaani in 1651 and between 1661 and 1666 converted the original wooden living quarters within the castle into stone residences with vaulted roofs. This transformation turned the castle into a noble residence and reinforced its administrative role. The castle remained the seat of the Kajaani Freiherrdom until 1681, when Sweden abolished the fiefdom in a process known as the Great Reduction, shifting the castle back to regional administrative and military use.

During the Great Northern War in the early 18th century, Kajaani and surrounding villages suffered burning in 1712. Efforts to strengthen the castle followed under Lieutenant Colonel Johan von Meurman, including upgrading defenses and adapting the towers to house cannons. In 1715–1716, Russian forces laid siege to the castle with overwhelming numbers. After approximately five weeks and facing severe shortages, the defenders surrendered in February 1716. The Russians broke promises for safe passage, deported defenders and civilians, and destroyed the castle by explosives the following month.

The castle returned to Swedish control in 1721 but was never rebuilt. A small military garrison occupied the ruins until the late 18th century. After Finland became part of the Russian Empire in 1809, the castle’s strategic importance declined further, though its island continued to function as a key river crossing point.

Interest in the castle’s remains revived in the 20th century. In the 1930s, archaeological excavations accompanied the construction of a new concrete bridge, recovering around 1,800 artifacts. Restorations were funded by the Finnish Parliament to stabilize the ruins. Later preservation work from 2001 to 2008 repaired walls and improved access, including the addition of a pedestrian bridge. Since 2014, Metsähallitus, a state agency responsible for managing natural and cultural sites, has overseen the castle’s upkeep.

Remains

Kajaani Castle was built primarily from locally quarried stone, chiefly granite, set with lime mortar that was likely produced using limestone from the nearby Melalahti area. Its main structure featured a rectangular plan roughly 39 meters in length, with external walls rising nearly 10 meters high and nearly 4 meters thick. The walls were coated externally with a thin white lime plaster, traces of which survive, while window openings were decorated with red paint, evidence of early aesthetic treatment.

The fortress was strengthened by two round artillery towers located at each end of the rectangle, as well as two rectangular battery positions. A gate tower stood on the northern side, providing main access to the castle island. The island itself was artificially expanded by piling earth and stones to create a stable foundation, with the castle walls built directly upon the rocky rapids. Access to the island was via two wooden bridges—one to the north and a longer one to the south—both spanning the river channels.

Initially, all internal buildings within the castle were made of wood. However, during renovations led by Count Per Brahe in the 1660s, timber structures were replaced with stone buildings featuring vaulted roofs. These stone houses followed a double-house design, with a central porch from which two separate rooms could be accessed. The chancellery was notable for its two-story construction, with a wooden intermediate floor and external stairs connecting the levels. Interior walls throughout the stone buildings were plastered with white lime, and the commander’s chamber featured a brick floor, while other rooms probably had wooden flooring.

Along the northern external wall, there were a series of rooms serving various purposes: gunpowder storage, living quarters, a porch, and a kitchen with an attached cellar beneath. From 1669 onward, the eastern tower’s upper floor was converted into a large hall known as the “great hall,” highlighting the castle’s function as a noble residence in that period.

Defensive improvements were made during the Great Northern War to withstand siege warfare. The upper floors of the towers were adapted to mount cannons. Moreover, a thick three-meter layer of peat was placed atop the walls to absorb artillery fire. Doors and windows were blocked to enhance protection, and obstacles were placed along the shoreline to deter attackers.

Over the 19th and 20th centuries, portions of the castle’s walls were dismantled to make way for bridge construction. Early restoration efforts in the late 1800s used brick patches to repair the decayed stone, but these were later removed and replaced with granite during more careful preservation work in the 1930s. Today, the ruins stand without roofs but have been structurally stabilized to preserve their outline and features. Continuous maintenance seeks to maintain the site’s cultural heritage while allowing visitors to appreciate the oldest parts of the fortress, including the remnants of its imposing walls, towers, and stone buildings.