Recently, Zagreb was struck by a strong earthquake. Damage throughout the city was tremendous due to numerous aged and vulnerable masonry buildings. Many damaged buildings are under a certain level of cultural heritage protection. Hence, reliable assessment and effective rehabilitation are important to preserve cultural significance and mitigate risk for human life. With that in mind, the procedure of a detailed condition assessment of the building under heritage protection is presented. A detailed historical background of the case study building is shown, and observed damage and conducted in situ tests are discussed. The nonlinear static seismic analysis performed in the 3Muri software is extensively elaborated. Four different levels of reconstruction according to new Croatian law are briefly presented. Additionally, several strengthening scenarios are proposed with various strengthening techniques.