Vault under the Palazzo del Podestà. It originally housed the city market and the benches of the notaries; later on, blasphemers were set on the pillory and hangings were performed under its arches.
A few centuries later, the vault acquired a religious significance when it was decorated with the terracotta statues of the saints protecting the city of Bologna: San Petronio, San Francesco, San Domenico and San Procolo.
Under the Voltone del Podestà there is an extraordinary acoustical effect probably due to the curved shape of the vault: you and a friend of yours can stand in opposite corners under the arches, face the corner and speak or even whisper and hear each other loud and clearly.