Regge calculus is the classical starting point for a bunch of different models of quantum gravity. Moreover, it is often considered a finite-element discretization of general relativity, providing so a potential practical scheme for numerical relativity. Despite these important roles, not many sample calculations have been studied. I will present one detailed example which, step-by-step, will show the power and the limits of this model. Many interesting aspects and open problems related to the Lorentzian structure of the discrete system will emerge.