The castle in Kruszwica was established on the initiative of the king Kazimierz Wielki after 1343 at a place, in which the hill fort was earlier already located. After being burnt in 1519 the castle was reconstructed and extended - it was then the seat of the castellan of Kruszwica and local starosty. It was again destroyed in 1657 during the war with Sweden, from the 18th century it was not used. In 1787 majority of castle buildings were dismantled, only the corner tower was left and it was reinforced in 1802. The area was levelled in 1867 and the park was established. In 1896 the tower was renovated and adapted to being visited by tourists. Another renovation was carried out in 1956.

The castle is located on the hill on the Ostrów Rzępowski peninsula, which was earlier an island on the Gopło lake. Castle is set on a rectangular floor plan, made of brick. It consisted of a residential building (not preserved) and a tall corner tower. Currently there is partly reconstructed Gothic tower from ca. mid-14th century, with the fragments of the peripheral wall. Octagonal tower, made of brick, was positioned on a plinth of erratic boulders. The interior was divided into six storeys of different heights.

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Accessible historic building. To enter the tower the visitor has to buy a ticket.