In the lower fort, a "Cutcherry" (administrative office) was added during Tippu Sultan's rule. Another interesting find in the arsenal is a quadruple mill made of masonry of depth and about diameter, which is inferred to be a device used for preparing gunpowder during Hyder Ali and Tippu Sultan's rule. In Kannada language, it is called 'Maddu Bisuva Kallu', which means "gunpowder grinding stone". The quadruple mill has four massive grinders with teeth or slots. These were rotated either by elephants or bullocks (in a central circular space) with an independent collection point for each of the four slots to collect the explosive gunpowder.