The Church of San Leopoldo in Follonica is one of the first cases of "iron architecture" in Tuscany. It is a concrete example of the productive relationship between technology, art and industry that was taking shape in the Grand Duchy in the first half of the 19th century, though with some delay compared to the countries beyond the Alps.

Designed by Alessandro Manetti and Carlo Reishammer, it was consecrated in 1838 in the presence of Grand Duke Leopold II. It consists of numerous cast-iron elements (the pronaos, the facade rose-window, apse, various interior furnishings, bell tower coping), manufactured by the division of artistic foundry that had opened in 1835 in the manufactory in Follonica. The use of iron in the building structure made it possible to grasp the expressive potentials of the material in the field of art.

In those years, the new technology – and we might say the new language – was also present in Florence: we need only think of the glass and cast-iron lantern of the Galileo Tribune or, in a different context, the two suspended bridges on the Arno, San Leopoldo and San Ferdinando (neither of which exists today).