The superb collection of five centuries of local painting in Siena's national picture gallery can easily convince you that the Renaissance was by no means just a Florentine thing—Siena was arguably just as important a center of art and innovation as its rival to the north, especially in the mid-13th century. Accordingly, the most interesting section of the collection, chronologically arranged, has several important "firsts." Room 1 contains a painting of the Stories of the True Cross (1215) by the so-called Master of Tressa, the earliest identified work by a painter of the Sienese school, and is followed in Room 2 by late-13th-century artist Guido da Siena's Stories from the Life of Christ, one of the first paintings ever made on canvas (earlier painters used wood panels). Rooms 3 and 4 are dedicated to Duccio, a student of Cimabue (circa 1240–1302) and considered to be the last of the proto-Renaissance painters. Ambrogio Lorenzetti's landscapes in Room 8 are the first truly secular paintings in Western art. Among later works in the rooms on the floor above, keep an eye out for the preparatory sketches used by Domenico Beccafumi (1486–1551) for the 35 etched marble panels he made for the floor of the Duomo.