Sir Walter Raleigh took possession on 1581, and he modernised the castle. The Earl of Broghill garrisoned his troops here during the Confederate War of 1641-1653.
The last occupants of the castle were the Courthorpe family in 1640.
The nearby Martello Tower was one of five such towers built in Cork Harbour during the Napoleonic Wars between 1810 and 1815.
The cache is a camouflaged tupperware box, at ground level.