The castle in Jasiniec was built in the 14th century by the Teutonic Knights on the site of the former hillfort of Pomeranian dukes. A pfleger subordinate to the Świecie commandry resided there. During the Polish-Teutonic wars, due to the border location, castle often changed membership, moving from hand to hand. In 1454 he eventually became the Polish property and became the seat of the eldership, getting into the hands of Jan Kościelecki. During his time there was a reconstruction from the destruction of the Thirteen Years’ War. Further transformations, this time in Renaissance stylistics, were made in the years 1540-1565 under the staroste Adam Walewski. As a result, the castle acquired the character of a comfortable residence, equipped with rare glass windows, painted doors, fireplaces, stoves, etc. In 1773, after the first partition of Poland, the Jasieniec eldership was abolished, and the castle was designated as the seat of the church for Prussian colonists. On this occasion, the ceilings and internal divisions were removed. In the nineteenth century it was finally abandoned and fell into ruin.
The castle occupied the top of the hill on the peninsula at the edge of the Castle Lake. It was preceded by a outer bailey, separated by a moat, about 15 meters wide and placed closer to the base of the headland.
The castle house in the late Middle Ages was 12,8×22,6 meters in size and was surrounded by a low defensive wall. Its walls were raised to a height of 5,5 meters from glacial erratic stones bonded with lime mortar, and higher parts from brick. The ground floor housed utility rooms, the representational halls were on the second floor, among them the “grand chamber” and the chapel. Above it was a residential level with four rooms. The highest, fourth storey with a defensive function was equipped with 22 arrowslits.
The castle has survived in the form of a ruin, deprived of the highest storey and internal walls. It belongs to a private investor, but despite his promises, he has not taken any serious security work so far.
Dzieje Świecia nad Wisłą i jego regionu, red. K.Jasiński, t. 2, Warszawa 1980.
Leksykon zamków w Polsce, red. L.Kajzer, Warszawa 2003.