The image shows the Prague Astronomical Clock, also known as the Orloj. This historic
masterpiece is located on the south wall of the Old Town Hall on Old Town Square in Prague.
It is a medieval astronomical clock installed in 1410, making it one of the oldest
working astronomical clocks in the world. The clock shows not only the time but also the
relative positions of the sun, moon, Earth, and zodiac constellations. It consists of three
main parts: the astronomical dial, the calendar dial, and the "Walk of the Apostles,"
a mechanical puppet show that takes place every hour. The astronomical dial, the oldest part,
was made in 1410 by clockmaker Mikuláš of Kadaň and Jan Šindel, a professor of astronomy.