Levyhalli (Plate workshop) was built to house a pump house, boiler room and workshops for the shipyard in 1917 on top of the repairs dock of the former galley shipyard. The building also had pneumatic systems and the necessary tools and equipment storage spaces, dressing rooms and offices.

The building is mostly in its original state; the skylight was altered probably in 1928. One partition has been demolished in the machine shop unit, which had divided the space into a machine workshop and forge press.

During the early years of Finland’s independence, the building was used as the machine shop of Suomenlinna Technical Board, where motor boats were repaired. In 1921, the Finnish Air Force aircraft factory (later the State aircraft factory) began operations in Suomenlinna, and the former space where ships had been repaired and built now became an aircraft assembly workshop.

The building served as an aircraft factory between 1921 and 1935.

In 1936, the aircraft factory left Suomenlinna, and all the spaces it had occupied came to be used by the State shipyard that had started operations some time earlier in 1930. The State shipyard and the State metalworks were merged after the Second World War to form Valmet, which occupied the building until 1985. After this, it came under the management of the Governing Body of Suomenlinna.

Today, the building hosts different events such as exhibitions and concerts in summer time.