Subjected to multiple conversions in times of adaptation for 19th-century Prussian administration purposes and restored in the 1920s and over the years 1969-1970, Saint Lawrence’s Church interior preserves historical painting ornamentation relics. In 2021, the Malbork Castle Museum commenced conservation studies of wall polychromy components, the early research stage involving efforts to establish the reach of original paintings and confirm recorded layer stratigraphy. Exposure sites were selected on the basis of a detailed photographic documentation analysis, successive interior décor stages having been duly recorded: early 20th-century restoration works to post-completion status to post-1969-1970 works condition. The comparison proved beyond reasonable doubt that successive renovations had obscured components of the sanctuary’s former painting ornamentation. Early conservation exposures confirmed the presence of historical polychromy beneath modern-day whitewash, allowing a number of phases to be tentatively identified for the interior décor development process at the Outer Castle church. The purpose of this paper is to present findings regarding changes to Saint Lawrence’s Church wall ornamentation – both historical and associated with conservation layouts in the first and second halves of the 20th century. A comparison of gradual décor transformations further allows observation of changes in ways of preserving and exhibiting sequential historical layers in historical space.