This tower was described in the Bible, but there was no proof of its existence. Robert Koldewey re-discovered Babylon and ruins of this great ziggurat after 1913. It was built during or after the reign of Chammurapi (1792 - 1750 BC). The ancient builders needed more than 17 millions fired bricks. The height of the tower was 91 m. The year 331 BC was the last for the tower. It was demolished, but never re-build.