 Little is known regarding these restorations, but it is assumed that the cupola (dome) had been reconstructed using pipes made of terracotta, making it lighter than the previous one, perhaps already damaged to the extent of justifying a reconstruction.After the disasters of the eleventh century, the restorations of the twelfth and thirteenth centuries focused on providing stability to the whole complex, rebuilding the pillars that supported the cupola and carrying out other interventions on the load-bearing structures (columns, towers).In this period, a lantern was added above the dome, supported by flying buttresses leaning against the towers.