The ancient church of San Tomaso was consecrated by the bishop prince of Trento, Corrado da Beseno, in August 1194 and was dedicated to assisting and treating the infirm, or contagious sick. For this reason the church and its annexe were built in the open countryside, along the road linking Arco to Riva. Medieval documents show that in the Trento area, in addition to the church of San Tomaso, there were three other leper hospitals in operation. The Riva complex, under the direct authority of the bishop of Trento, was commissioned by Odorico the elder, signor of Arco. Although traces of the hospital walls have disappeared, incorporated into other buildings, the church of San Tomaso has preserved its linear Romanesque structure perfectly.