Roman Catholic Archdiocese of Siena-Colle di Val d'Elsa-Montalcino  The Archdiocese of Siena-Colle di Val d'Elsa-Montalcino () is a Roman Catholic archdiocese in Tuscany. The seat of the archbishop is the Cathedral of the Assumption in Siena. Until 1459, the diocese was immediately subject to the Holy See (Papacy), and its bishops attended the Roman synods. In 1459, Pope Pius II made Siena a metropolitan archbishopric. From September 1407 to January 1408, Siena played host to the papal Court of Pope Gregory XII of the Roman Obedience. In 1423, Siena was host to what was announced as a general council of the Church. Such meetings had been mandated by the Council of Constance, and, though Pope Martin V was most reluctant to have another council like Pisa or Constance, he authorized the assembly to meet in Pavia in the Spring of 1423. On 22 June, however, alleging the presence of the pestilence in Pavia, the Pope transferred the council to Siena. On 21 July 1423 the Council reopened in Siena, though there was only one general session, on 8 November. Work continued until the papal legates dissolved the council on 26 February 1424, though the papal bull of dissolution was not published until 12 March. On 22 April 1459, Pope Pius II issued the bull "Triumphans Pastor", in which he raised the diocese of Siena to metropolitan status, and assigned to it as suffragans the dioceses of Soano, Chiusi, Massa, and Grosseto. The Second Vatican Council, in order to ensure that all Catholics received proper spiritual attention, decreed the reorganization of the diocesan structure of Italy and the consolidation of small and struggling dioceses. In 1980, the diocese of Montalcino claimed a Catholic population of 24,500 persons. Colle di Val d'Elsa had slightly over 60,000. On 18 February 1984, the Vatican and the Italian State signed a new and revised concordat. Based on the revisions, a set of "Normae" was issued on 15 November 1984, which was accompanied in the next year, on 3 June 1985, by enabling legislation. According to the agreement, the practice of having one bishop govern two separate dioceses at the same time, "aeque personaliter", was abolished.