Unreinforced masonry structures are particularly vulnerable to seismic events. Their seismic vulnerability stems from the brittleness of the material and the insufficient connectivity with the neighbouring structural components. This results in the formation of local collapse mechanisms, whose dynamic motion can be resembled by a rocking block. Rocking motion constitutes a well-known, yet still challenging, problem in earthquake engineering due to its highly nonlinearity and sensitivity to various attributes of the seismic signal. This work attempts to shed light on the dynamic behaviour of rocking blocks using both experimental and numerical methods. Specifically, using a recorded earthquake, 70 shaking table tests are conducted on limestone blocks, and fragility curves of their maximum response are constructed. Moreover, two nominally similar blocks are tested under the same excitation to examine the repeatability of their experimental response. The study continues with the evaluation of different intensity measures able to describe the vulnerability of rocking blocks. Finally, two numerical models that consider a rigid and flexible contact interface are adopted. This allows for a deterministic and statistical comparison of the numerical predictions against the experimental results, revealing the merits and shortcomings of the numerical models in predicting the rocking response.