The building in which is the seat of the Trentian Diocesan Museum, commonly called Palazzo Pretorio, was the late Middle Ages residence of the bishops of Trento. In an unclear epoch, between IX and X century, the basilica of S. Vigilius assumed the function of the town cathedral, a role previously assigned to the "ecclesia intra civitatem" referring to the Passio Sancti Vigilii, located in the area of the church of S. Maria Maggiore. It was then that the episcopal residence was transferred from its oldest site to the area between the ruins of the Porta Veronensis and the head of the basilica vigiliana: here was erected the "palatium episcopatus", equipped with its own chapel dedicated to Ss. Biagio and Lucia. The building presumably consisted of a series of houses and walled courtyards; the part adjacent to the cathedral, the so-called 'Castelletto of Bishops', was destroyed by a fire and rebuilt by Frederick Spade (1207-1218).
Around 1255 Egnone Appiano moved the episcopal residence to the fortress built by Sodegerio of Titus, imperial podesta, on the hill of Malconsey. Thus began the progressive abandonment of the old "palatium episcopatus", partially used as a seat of the Court of Justice and pretura. In 1533 Cristoforo Madruzzo ceded the part toward the Torre di Piazza in the Monte di Pietà which, in turn, sub-leased the second floor to the consuls of the city and the College of doctors. In 1676 Sigismund Alfonso Tuhn promoted the restoration of the building, unifying the facade that lost the original Romanesque configuration given by the presence of double and triple lancet windows. In 1780 the Municipality demolished the Renaissance loggia that rested on the tower and entrusted it to the arch. Claudio Carneri had the task of integrating this space with the rest of the building with a new series of works. Until 1883 the palace was the seat of the i.r. Circular Court; in consequence of the i.r. Direction of the Genio and in the second world war the regional Command of the Corps of the state forests. In the fifties, finally the part was purchased by the Cathedral. After a radical restoration, designed to recover the ancient Romanesque facade, and the restoration of the building, in 1963 the palace was used as a permanent seat of the Diocesan Museum of Trento.