Italy is one of the countries in the world with the largest concentration of architectural cultural heritage, most of which are churches, bell towers, and religious buildings in general. This paper deals with the issues of the analysis and evaluation of the seismic behaviour of slender masonry structures, taking as the subject of analysis Giotto's Bell Tower in Florence (Italy). The seismic vulnerability has been analysed according to the current Italian legislation and the guidelines for the evaluation and reduction of seismic risk of cultural heritage. For this purpose, the bell tower was analysed using three evaluation levels: simplified methods (EL1), a kinematic analysis (EL2), and, finally, a finite element analysis (EL3). For each methodology, the level of seismic safety obtained by comparison with the local seismic demand has been evaluated.