A powerful symbol of the magic of Prague, the clock represents the passing of time and life. When the hour strikes, Christ appears with the twelve apostles, Death, the Turk, the Jew and Vanity. The cock crows at the end the display. The clock was installed in about 1410 by the royal clockmaker Nicolas de Kadan and a professor of mathematics and astronomy from the University of Prague. The three hands on the central clock face indicate the position of the stars according to medieval cosmology. The lower face is a wonderful calendar showing the months of the year.