The Cemetery is the last monument on Piazza del Duomo, its long marble wall flanking the northern boundary and completing its shape. It was founded in 1277 to accommodate the graves that until then were scattered all around the Cathedral. Archbishop Federico Visconti wanted the building to be a “large and dignified, secluded and enclosed place”. This is how one of the oldest Christian Medieval architectures for the devotion of the dead came into being.
https://www.opapisa.it/en/square-of-miracles/camposanto/