The National Picture Gallery is considered to be one of the finest museums in Tuscany and holds many great works. Paintings include: the Madonna of the Franciscans by Duccio di Buoninsegna, and the Nativity by Lorenzo Lotto, as well as works by Lorenzetti, Simone Martini and Francesco di Giorgio Martini. The collection, consisting of Sienese paintings from the 13th to the 17th centuries was begun by Abbot Giuseppe Ciaccheri in the late 18th Century, with works later added from dissolved churches and monasteries, bequests and storehouses.