The Torino Esposizioni complex consists of the main Hall B and the smaller adjacent Hall C, both designed and constructed by Pier Luigi Nervi (1947-1948, and 1950). In this work, Nervi combined for the first time his personal technique of ferrocement in a large-scale project with an extensive use of prefabrication. The first part of the paper presents a FE numerical analysis aimed at the evaluation of the seismic behaviour of the Hall B, in the light of its modal features. Based on numerical strategies already applied to Hall C within a previous study, optimal sensor placement solution will be extended to the more complex Hall B, taking into account the possible effects of non-structural elements.