Ok This clock is sersiously cool. Its an Astronimical Clock. it has so many things to tell you. like time in 24 hour, month, day, tide changes along the river thames, whether the moon is full or not, astonomical months... It has been at the palace since about 1478 the thing is in this clock the sun is revolving around the earth which means it was built before copernicus proved that the earth and other planets revolve around the sun, not the other way.