The impressive original structure has many elements in cast iron. About thirty tons of metal used for pillars, windows frames, ellipses and decorations of various kinds. Everything was cast in the Carlandi foundry of Tivoli during its heyday: it was certainly the most prestigious work ever carried out by this foundry. The restoration, given the conditions of total disrepair of the building, required the complete dismantling of the parts concerned. The missing parts or those considered as no longer recoverable were reproduced, thanks to a specific effort of classification, documentation and research.