Here I show a close-up of the Prague astronomical clock (Prague orloj), a large medieval astronomical clock which is mounted on the southern wall of the old town hall in the old town square. As you can see, it has three components: (i) the astronomical dial, representing the position of the sun and moon in the sky and displaying various astronomical details; (ii) "The Walk of the Apostles", a clockwork hourly show of figures of the apostles and other moving sculptures; (iii) a calendar dial with medallions representing the months. It is a mesmerizing piece of art and a true symbol for Prague and for the Czech Republic.