After the Zagreb earthquakes in March of 2020, around 25, 000 buildings were estimated damaged, most of them being in the historic city center. This fact is not that surprising since most of the city center buildings are unreinforced masonry structures that have not been assessed in quite some time and usually no retrofitting methods were ever applied. The rapid post-disaster assessment began the same day after the first earthquake occurred. Through mostly visual assessment methods, the basic idea is to identify the safety and usability of buildings in general. This type of assessment was also conducted in one of the oldest Croatian cultural institutions, Matica Hrvatska. It is a building of great historical significance and cultural value, as is most of the city center. Accordingly, this building was constructed with no consideration given to seismic events and with the use of traditional materials and building techniques. In the scope of this paper, urgent actions that were taken are shown with problems and challenges that occurred. Furthermore, the decision-making process after an earthquake is elaborated. In addition, a numerical model is developed in 3Muri software for structural modeling. Non-linear static pushover analysis is performed, and possible failure mechanisms are examined. Furthermore, real-life damage is compared to the software results, and a conclusion process of the building’s usability is explained. In the end, the results obtained are analyzed and conclusions regarding the efficiency of the used software are drawn.