During the Gustavian period, three large gunpowder magazines were built in Suomenlinna. The Susisaari gunpowder magazine, built in 1776–1778, is one of the two remaining gunpowder magazines.
The large vaulted openings at the ends of the Susisaari gunpowder magazine have been bricked up. The architecture from the Swedish period can still be seen in the interior: the grand, barrel-vaulted room is encircled by a low, vaulted defence passage equipped with embrasures for rifles. The only entrance to the inner part of the magazine was through the surrounding passage, from the southern end of the building. The walls and vaults were equipped with a skilfully made ventilation system to keep the gunpowder dry.
The roof structures were destroyed in a fire caused by the bombardments during the Crimean War. In 1878, the magazine was completely covered in huge layers of earth and dirt, leaving only the north-eastern façade visible. During the Finnish period, the gunpowder magazine was used as a storage space and a potato cellar. A door opening was made in the inner wall of the magazine end. In 1999, the gunpowder magazine was renovated for use as a conference and banquet facility.
