Steel is an alloy of iron and other ingredients, processed in furnaces to remove between 96 and 99 percent of the carbon. The first steel is thought to have been made in the civilizations around the Mediterranean Sea sometime after 3,000BC. Wrought iron and later cast iron were used much more extensively in primitive architecture; fine steels were used primarily for weapons such as swords. For hundreds of years the secret of steelmaking was lost, and was not to be rediscovered until 1740. It was another 150 years before steel frames were used in buildings, allowing them to reach unforeseen heights. There are many varieties of steel, including stainless steel, used for different industrial purposes.
