Massive Cache of 450 Medieval Cannonballs Unearthed at Belgian Construction Site May Be First of Its Kind Worldwide

Archaeologists working at a construction site in the coastal Belgian city of Nieuwpoort have uncovered a remarkable cache of approximately 450 medieval stone cannonballs, a find researchers are describing as “highly unusual” and potentially the first discovery of its scale ever documented. The trove offers a rare window into late medieval warfare and the turbulent military history of Flanders.

The discovery was made during preparatory excavation at a building project in Nieuwpoort, a historic port town on the Belgian North Sea coast that has long been a strategic military crossroads. Archaeologists working with the regional heritage agency encountered the carefully stacked projectiles in what appeared to be a dedicated storage pit or munitions dump. The sheer volume of the find — roughly 450 stone balls in one concentrated location — sets it apart from typical medieval artillery recoveries, which usually involve only a handful of projectiles scattered across battle sites or fortress ruins.

Nieuwpoort’s strategic location at the mouth of the Yser River made it a repeated target throughout the medieval and early modern eras. The town was besieged multiple times during the Hundred Years’ War and later conflicts between Burgundian, French, and Habsburg forces. Stone cannonballs of this kind were typically hewn from locally available rock and fired from early gunpowder weapons known as bombards — massive siege guns that began replacing traditional trebuchets and catapults across Europe in the 14th and 15th centuries. The variation in diameter among the recovered projectiles indicates they were manufactured for different calibers of artillery, pointing to a well-organized military supply operation.

Researchers now plan a detailed petrographic analysis of the stone to determine its geological origin, which could help establish whether the ammunition was locally produced by defenders or transported by an invading army. Carbon dating of any organic residue, combined with stratigraphic analysis of the surrounding soil, should narrow the precise historical moment of the cache’s burial. The artifacts are expected to be cataloged and eventually displayed in a regional museum, with some possibly traveling to international exhibitions given the unprecedented scale of the find.