The age of the moon on the Jubilee clock of the Zimmer tower.The Zimmer tower (Dutch: Zimmertoren) is a tower in Lier, Belgium, also known as the Cornelius tower, that was originally a keep of Lier's fourteenth century city fortifications. In 1930, astronomer and clockmaker Louis Zimmer (1888–1970) built the Jubilee (or Centenary) Clock, which is displayed on the front of the tower.