Augustine Cathedral, the earliest church in Paris built with iron, is not special in appearance. When you enter the cathedral, you can see the construction of cast iron supporting the top of the cathedral. It originated from the fact that the technology of iron had just been paid attention to. At that time, people's aesthetic still stayed in the classical period and could not accept the bare cast iron. So even if it was made of steel, it had to be covered with a layer of stone. Generally speaking, this church is of the stable type.