he castle in Buk was built by the Flemming family line in the beginning of the 15th century. It was located 0,5 km to the south-east of the 13-th-century fortress of the Plötz family. The casle was situated on a human-made 5-metre high mound. Beneath the mound an outer castle was founded. The complex was surrounded by a water-filled moat. The discription of the castle in the historic record of 1500 (judicial act - arbitration agreement - concerning a title to the castle in Buk of two Flemming family lines) mentioned an entrance gate probably in the area of the outer castle, a dwelling house adjacent to an outer wall and a gate tower.
The 14-th-century cavetto and barrel vaulting have been preserved to our times in the buildings which have remained of the castle. They house a PAN (Polish Academy of Sciences) library.