The heaviest guns in the forts around Amsterdam (except for the 15 cm turrets in Velsen were the 10,5 cm guns. The fortress guns were called "10 cm snelvuur" or 10 cm rapid fire. These guns were installed in the traditore batteries of the first generation forts. Only one of these guns has survived and is now displayed at the artillery museum at 't Harde. It has been restored and is in a perfect condition. The firing room has been reconstructed, including all the fire instructions on the wall and the small panorama. For more information about the artillery museum click here.