The castle was situated on the eastern bank of the Drwęca River, on the outer side of its bend. It consisted of the seat of the convent – the upper ward, and the outer bailey adjacent to the south and east, thanks to which the northern part was the least protected side. A town developed to the south-east of the castle, fortified from around the mid-fourteenth century.
The upper ward was built on a square plan with dimensions of about 45×45 meters, made of bricks on a stone foundation. Its four wings were equipped with three corner, projecting, square turrets with side lengths of 4.7 meters, and from the south-west with a small dansker tower, protruding towards the river. On the northern side, instead of the turret, there was an almost 50-meter-high tower, 10.8 meters in diameter, separated from residential wings. From the south-east side, a castle gate adjoined the tower, preceded by a foregate and a bridge over the moat. The foregate was not covered with a roof. In terms of military technology, this meant switching from passive to active defense, defending the gate instead of retreating to the bergfried, when the rest of the castle was already in enemy hands.
Entrance to the main tower was only from the wall-walk porch. The timber porch also surrounded the entire tower, allowing to get around the entire perimeter of the castle. The tower is hexagonal in the lower part, above passes into a lofty octagon, crowned with an observation deck with an octagonal superstructure. In contrast to the main tower of the castle in Świecie, there is no machicolation on the upper porch of the tower, only battlement was used. The crown of the tower was a demonstration of the power of the Order, which was emphasized by white, plastered blendes on two levels, and a heraldic shield with a black cross. The lower parts of the tower were also decorated, covered with a diamond net made of black zendrówka bricks. The interior has been divided into 13 floors, three of which were chambers located below the entrance zone, serving as a prison and guard rooms. The storeys were connected with each other only by ladders (no stairs were used in the wall thickness).
The functions of individual rooms are difficult to recreate today, but the typical division into the economic ground floor, the representative and residential upper floors and the warehouse and defensive attic was certainly used. In the north-east range of the upper ward there were probably the main rooms of the convent: the refectory and the chapter house. In the south-east range there was the castle church of Corpus Christi and the Virgin Mary, while in the south-west range: chambers of the commander, senior Teutonic dignitaries, a chaplain and a dormitory. The representative function of the chambers located there is confirmed by large ogival windows. The sacristy was placed in one of the corner towers. In the ground floor, according to early modern description there was a kitchen. Most likely it was located in the south-west wing, because in the north-west relics of the hypocaustum furnace were discovered, heating the upper chambers with warm air. Another such furnace was in the castle basement under the refectory, while the other basement rooms served as storage. Access to them led directly from the courtyard through the cellar’s necks. In the north-east and south-east, they were rebuilt at the beginning of the 15th century and connected into one underground passage running along the eastern corner of the courtyard, to which the entrance led from the north.
The castle church was an aisless, five-bay structure covered with a stellar vault. It had a very rich sculptural decor: the capitals of vauls shafts, bosses and figures of the apostles were placed on the walls under the canopies, and the entrance portal was in an open porch, the walls of which were decorated with blind traceries and bas-reliefs.
The courtyard of the upper ward was surrounded by a brick, two-story cloister, the lower storey of which was supported by granite columns. At least at the north wing in the ground floor it had solid walls with rooms inside. The elevations of the castle were over 17 meters high. The entire upper ward was surrounded by low perimeter walls with one corner cut off, forming a zwinger of about 10 meters in width. From the south-west there was the aforementioned dansker, accessible from the main castle by means of a timber, suspended porch, and in the western corner a four-sided tower. Around 1415 it was (together with the tower at the outer bailey) transformed into a cylindrical form, adapted for the use of firearms. During this period or a little earlier, at the end of the fourteenth century, the commander’s house with the hypocaustum furnace was erected in the north-eastern part of the zwinger.
From the east and south, a large L-shaped outer bailey adjoined the upper ward. Two gates opposite each other led to it, and the perimeter of the walls was reinforced by four-sided towers in the northern and eastern corners. The town fortifications were not linked to the castle, because they were separated by a small stream. The economic buildings were attached to the inner faces of the outer bailey walls. According to early modern descriptions, it housed stables, a half-timbered carriage house and a brewery (malt house). There was probably also an infirmary, woodcarving house, footwear workshop, and bathhouse at the outer bailey.
