The Palazzo Pubblico, the town hall of Siena, stands at the lower end of the steeply sloping Campo, with the Piazza del Mercato at its rear. The building project was initiated in the 1280s, when it was decided to combine in one building the Customs offices, the Mint and the Council offices, together with the residence of the Podestà. The new palazzo was designed to face the Campo. In 1354 the Cappella di Piazza was built at the base of the tower; in 1468-1470 its porch received a Renaissance canopy by Antonio Federighi. In 1680, perhaps under the direction of the architect Giovanni Battista Piccolomini (1623-1697), a storey was added to each of the lateral wings of the Palazzo Pubblico, designed to correspond stylistically with the rest of the building.