As Cardinal Domenico della Rovere wrote, the Lower Church should be considered a church in its own right, which the cardinal intended to serve as a mausoleum and, together with the Upper Church, replace the memory of the demolished medieval churches in the minds of the worshippers. The size and architectural dignity of this enormous space make it one of the emergent hubs – long kept in obscurity – of the cathedral church of Turin and was originally an integral part of the Upper Church. The church has retained its Renaissance form, characterized by outer walls with rectangular windows overlooking the piazza that illuminate the nave, marked by massive central piers and a vaulted ceiling that distinguishes the low space of the underground area. The keystone bears the crest of Cardinal Della Rovere, who built the new cathedral. The Lower Church faithfully mirrors the plan of the floor above, from which it is accessed via stairs in the outer wall. There was also an entrance from the outside, beneath the stairs on the façade. Only the room initially used as a sacristy in the 16th century was profoundly conditioned by the presence of the foundation piers of the chapel of the Holy Shroud. It is separated from the nave by an unbroken wall, erected at the end of the chancel. From the 16th to 19th century it was used to house the remains of the Savoy family, as testified by the large crosses found on the plastered surfaces. During these excavations the layout of the Early Christian basilica of San Giovanni was traced. Together with the finds at Santa Maria, it offers new information on the plans of three Early Christian churches that existed before the current cathedral.