The structure of the Mole Antonelliana is unique in its kind because of the technique used by Alessandro Antonelli. The lower part is made of bricks, with a square base. The hall is typical of Roman temples with neoclassical columns. The pitched roof runs on all sides and is connected to the central module, divided in two sections. The lower roof consists of 20 columns on each side and the higher one is enriched with semicircular glass windows. At the top of the roof there is a big dome, made by a sort of shell with very thin walls.