The face of the Prague astronomical clock in the Old Town Square of Prague, the capital of the Czech Republic. The dial takes the form of a mechanical astrolabe, a device used in medieval astronomy, and represents the standing Earth and sky; surrounding it are four moving components: the zodiacal ring, an outer rotating ring, an icon representing the Sun, and an icon representing the Moon. The clock was installed in 1410 by clockmakers Mikuláš of Kadaň and Jan Šindel.Photograph: Andrew Shiva