The Marble Room functioned as the second vestibule in the state apartment and is the oldest interior in that apartment. It was furnished from 1640-42, during the reign of Ladislaus IV, according to a design by Giovanni Battista Gisleni and it was renovated by Jakub Fontana in the years 1769-71. Fontana did not make any changes to the basic elements of the original architectural design; he added twenty-two portraits of Polish kings, a ceiling painting by Marcello Bacciarelli and André Le Brun's statue of Justice and Peace over the mirror.

The final decision to begin the reconstruction was made in January 1971. The construction works started in September 1971. The first stage of the project – body of the building in an unfinished state – was completed by July 1974. In 1977 first interiors were ready. The next ones were delivered in August 1984, during an official ceremony of opening of the Castle to the public. Handing the reconstructed Royal Castle to the nation was an act of honouring all of those, who, during the occupation, with the greatest dedication and risking their own lives, saved the Castle and the Castle art works for the future generations.