According to the original design from 1893, the western part of the Governor's Palace complex housed auxiliary rooms for servants and maintenance staff necessary for the smooth functioning of the operating and private quarters of the governor’s residence.

A simple outbuilding was located in the westernmost part of the complex and connected to the Palace with a gallery with glass-paned semi-circular arcades and a roof terrace, just like the garden pavilion on the eastern side.
The outbuilding housed stables, hay and tool sheds, servant quarters and a kitchen. The corridor through the enclosed gallery space was used by the servants as the main communication route between the Palace and the auxiliary rooms in the outbuilding.
The roof terrace on the gallery is at the level of the Palace's first floor and connected with the terrace on the gallery of the eastern wing by a paved path along the Palace’s rear (northern) wall. The western gallery space terrace could be accessed from the corridor on the Palace’s first floor, where the guest rooms were originally located.

When the Palace became seat of Italian rule (1924), the ground floor of the outbuilding was used as a garage, and a radiotelegraph station was set up on the first floor.
During the extensive restoration of the complex in 1938, the outbuilding was remodelled and converted into apartments for drivers on the first floor, while the radiotelegraph station was moved into the ground floor of the main building. Communication with the Palace through the gallery was preserved.
For a brief time after World War II, a part of the outbuilding served as a cafeteria for a secondary school dormitory. After nationalisation in 1948, it was remodelled and three housing units were arranged. In 1955 an additional floor was raised on the northern section of the outbuilding and four additional housing units were arranged. The remaining parts of the Governor’s Palace complex were used for cultural purposes under the management by the Vladimir Švalba Vid Culture Hall.
By detaching the buildings of the Governor’s Palace complex, communication route through the western gallery was disrupted and this space, along with a part of the park in front of the gallery, was rearranged into a lapidarium managed by the Museum of the Croatian Littoral. The most recent reconstruction of the lapidarium took place in 2005.
Even though the entire Governor’s Palace complex was granted the status of cultural monument in 1961, and despite fierce opposition by architectural experts, the decision to demolish the outbuilding was made in order to construct a new building for the Museum of the National Revolution in its place. The tenants were evicted and the building was demolished in 1973.

The new building, one of only three examples of museum architecture in the former Yugoslavia, was built in 1976 based on designs by architect Neven Šegvić (Split, 26 Jan 1971 – Split, 13 Nov 1992). In 1994, with the closing of the Museum of the National Revolution, it became the seat of the newly formed The City of Rijeka Museum. The space requirements for the new museum were detrimental to the original design and led to adaptations that impacted the interior harmony.