The cathedral of Modena is a model of the Romanesque style not only for its complete architectural structure , but also, as we will see, for the richness of the sculptural decorations, with a prevalent educational function, which integrate perfectly with the various parts of the building. Begun to build in 1099, the cathedral of Modena has very close relationships between the interior and exterior of the building. The three naves clearly correspond to the salient façade . The external buttresses, on the other hand, coincide with the division into spans by means of beam pillars. The three-light windows of the women's gallery have an external correspondence with the loggias on the median plane of the facade. The alternation of massive columns and bundled pillars creates the effect of a well-rhythmic volumetric space. The brilliant inventor of this building was Lanfranco, who envisioned a dense weave of blind arches on the outside , including groups of three-light windows at the top, along the sides and on the apses, which correspond to a long open loggia along the external perimeter. Intimately connected to the architectural program of the church is Wiligelmo's sculptural decoration, whose direct participation in the works together with Lanfranco, as an architect, and not just as a sculptor , has even been suggested . Together or shortly after Wiligelmo's work, another surprising presence is recorded in the Modenese construction site, that of the so-called Master of the metopes, whose metopes were likely to crown the external top of the building. The cathedral of Modena represents a model of Romanesque style, capable of establishing a close relationship between inside and outside. A building that some of the most brilliant artists of the Middle Ages worked on.