Built in the 19th century, the drill hall was erected for the purpose of "protecting the soldiers' fancy Prussian uniforms from the rain". Today, it houses an exhibition of historic cannons, including 16th-century state guns. The weapons collection also reminds visitors that Spandau was Prussia's armoury from the 18th century onwards. Not far from the citadel, rifles and guns were once built and gunpowder was manufactured. During the First World War, up to 70,000 people worked here in the armaments industry.