Tanks at Historic Sloss Furnaces in Birmingham, Alabama. From Wikipedia.Org: "Sloss Furnaces is a National Historic Landmark in Birmingham, Alabama. It operated as a pig iron-producing blast furnace from 1882 to 1971. After closing it became one of the first industrial sites (and the only blast furnace) in the U.S. to be preserved and restored for public use. In 1981 the furnaces were designated a National Historic Landmark."