The astronomical clock in Old Town Square has kept time for over six centuries and continues to keep accurate time to the present day. It is amazing how a timepiece as complex as the astronomical clock could be built in a time of relatively low technology. The clock shows three individual sets of data. It shows the revolutions of the Sun, the revolutions of the moon, and the revolutions of the stars. The movements of the clock are provided by large wheels mounted on the same axle. The first gear contains three hundred and sixty-five teeth and drives the zodiac. The second gear contains three hundred and sixty-six teeth and rotates the sun indicator. The third gear drives the moon pointer and contains three hundred and seventy-nine teeth. The clock also contains a half silvered and half black ball that rotates and displays the phase of the moon. The clock is divided into red and blue halves representing day and night. Two images stand on each side of the clock faces. These images are allegorical and represent vanity, greed, death and lust. The bones of the skeleton rattle as the clock strikes the hour, and carvings representing the 12 Apostles show themselves in procession in the blue windows above the clock.