The cannon tower was built in the eastern corner of the perimeter wall right next to the shoreline. The water traffic of the strait of the lake Vanajavesi was easily monitored from the two-story tower. From the outermost firing holes, cannons could be fired along the side of the perimeter walls if the enemy tried to get in front of the perimeter wall.

Work on the masonry of the cannon tower, or rondelle, on the banks of the Vanavesi lake began in April-May 1559. The work was supervised by Henrik von Cöllen from North Germany, who had previously worked on the crown's fortifications in Turku in Finland, Kalmar and Strängnäs in Sweden. Between 10 and 13 masons worked on the site at any one time. The peasants of Häme supplied the site with lime, bricks and grey stones. In addition, the peasants had to carry bricks, haul grey stones and lift them up on scaffolding for the masons. By September 1559, the tower was finished and the site gradually quietened down.

Over the years, the tower fell into disrepair, but in 1988 it was roofed and opened to the public, restored. The intermediate floors of the turret have not been restored, so that visitors to the castle can now see all the way to the ground floor of the turret from the upper level.