The roofs of the Imperial Palace buildings deserve special attention. Originally, the roofs were made mostly of wood, and to prevent the tiles from sliding, wooden nails were used. However, without lightning rods, the palace roof would easily catch fire. Therefore, some alchemists suggested that symbols of the fish-tail star could be installed on the roof to prevent fire. Later, these symbols were replaced by glazed tiles which were shaped like lucky animals, some of these, like dragons, were imaginary.Read more