The paper presents the findings of conservation-restoration explorations of the building located in the south-western corner of the former county prefect’s castrum plateau, recognized as the granary of the counts of Celje in the eastern part, and the Varaždin general headquarters’ armoury in the western. During the explorations, the published references, as well as the available archival materials have been processed and analysed. During field work, methods of visual analysis and probing of the construction material, the plastered and paint layers have been used. Apart from conservation-restoration works, geophysical explorations were also undertaken, as well as the test archaeological probing on certain locations. The present building is located within the perimeter of the estate that had belonged, since its very foundation, to the fortified royal county prefect’s castrum. That is why it seems impossible that such an estate could hold within the property of a citizen, which is one of the arguments of older historiography for attributing the lower part of the building to the granary of the Counts of Celje. The other argument concerns the stone wall frames with gothic profiling, for which the exploration findings from the building’s interior have unequivocally shown that they were added at a later time.