 Ziggurats were elevated temples constructed by the Sumerians between the end of the 4th millennium BC and the 2nd millennium BC, rising in a series of terraces to a temple up to 200 feet (61 m) above ground level. The Ziggurat of Ur contained about three million bricks, none more than 15 inches (380 mm) in length, so construction would have been a huge project. The largest ziggurat was in Babylon, and is thought by some to be the Tower of Babel mentioned in the Bible. It was destroyed by Alexander the Great and only the foundations remain, but originally it stood 300 feet (91 m) high on a base about 660 feet (200 m) square. Sun-dried bricks were used for the interior and kiln-fired bricks for the facing. The bricks were held together by clay or bitumen.
