The castle in Bobrowniki may have been built around the middle of the 14th century from the foundation of Władysław Garbaty, the Duke of Dobrzyń, although archaeological studies postpone the date of its construction to the end of the 14th century. In this case, its builder could be Prince Vladislaus II of Opole, who owned the Dobrzyń land as a feud in 1379-1392. Finishing works could also be carried out by the Teutonic Knights who occupied the local lands in the period 1392-1404, although the preserved documents only provide information about their minor works being carried out at that time.
During the wars of the second half of the fourteenth and the beginning of the fifteenth century, the castle repeatedly passed from the hands to hands. In 1391 it withstood the siege of the Polish army, then returned to the Polish king, but in 1409 it was again captured by the Teutonic Knights. Finally, after 1411, it returned to Poland and on the initiative of king Władysław Jagiełło was considerably expanded. When the Second Peace of Toruń in 1466 ended Polish-Teutonic war, the castle lost its military significance and became the seat of the staroste. In the seventeenth century it was ravaged by the Swedes, although, as the graphics from 1627 show, it was previously partly ruined. Eventually, it was pulled down in the 19th century.
The castle was located on an artificial embankment directly on the right bank of the Vistula. In its close vicinity there was the mouth of the small river Gryzki. The earliest building was a square with a side of about 46.5 meters. It consisted of a main house based on the north-west curtain, a cylindrical tower with a quadrilateral base measuring 10.7 x 11.2 meters and a low gatehouse. The latter was located in front of the north-eastern curtain, on a plan similar to a square measuring 10.5 x 11.5 meters. The interior of its ground floor and probably the vaulted gateway with a passage of about 3 meters wide, housed a small, vaulted guard’s room. Perimeter walls with an impressive thickness exceeding 3.5 meters, were reinforced from the outside with buttresses, at both corners and over the curtains. In addition to the main gate, two smaller postern gates were opened in their course. The castle house measured 15 x 46 meters, was a single-bay building, with two above-ground floors and basement, covered with a gable roof. At the basement level, the interior was divided into three rooms, and this division probably also was repeated on the upper floors. A second, smaller building was located between the main tower and the above mentioned house, along the southeastern curtain of the wall. In addition, timber buildings at the north-eastern section of the wall, auxiliary with economic functions, could also function.
In the 15th century, the castle was expanded of a perimeter of external walls, located approximately 12.5 meters from the main perimeter and also reinforced with buttresses. Interestingly, they had a considerable thickness, similar to the inner ring of fortifications. As the gatehouse had side postern gates, before the construction of the second brick perimeter, could exist external fortifications in the form of a palisade. In the 15th century, the gate was also extended, and small towers were built in the corners of the second circuit, perhaps adapted for fire defense. The outer zone of defense was an irrigated moat surrounding the castle from the land side. Later reconstructions, maybe even late medieval, were associated with paving the courtyard and building earth ramparts that protected the castle from the north and east.
Currently, only the elements of the defensive walls, mainly the northern and southern part, as well as the relics of the tower, which in the highest place has been preserved to a height of 11.8 meters, are a trace of the former splendor of the building. Picturesque ruin is open to visitors.
Leksykon zamków w Polsce, L.Kajzer, S.Kołodziejski, J.Salm, Warszawa 2003.
Pietrzak J., Zamki i dwory obronne w dobrach państwowych prowincji wielkopolskiej, Łódź 2003.