Cast Iron. The Chinese used blast furnaces for making cast iron as early as the fourth century B.C.E. The largest cast-iron building was a temple constructed in 688. Ordered by Empress Wu Zhao, this 284-foot-high building was in the form of a 3-story pagoda (300 square feet), and a 10-foot cast-iron phoenix covered in gold plate was on the top of the building. In 695 Empress Wu ordered the erection of an octagonal cast-iron column known as the "Celestial Axis Memorializing the Goodness of the Great Chou Dynasty with its Numberless Areas." This 20-foot-high column was on a base of cast iron 170 feet in circumference. In 954 the emperor of the Later Zhou Dynasty (951-960) ordered the building of the Great Lion of Zangzhou as a memorial of his military victory over the Liao Tartars. This remarkable object was 20 feet high, 16 feet...