Description from Prague TV
The Prague Astronomical Clock (Pražský orloj) is mounted on the southern side of the Old Town Hall, on Old Town Square, and is a popular tourist attraction.

The Orloj consists of three main elements: the astronomical dial, representing the position of various celestial bodies; an hourly show featuring moving clockwork figures, known as the "Walk of the Apostles"; and a calendar dial decorated with painted discs representing the months.

On the hour, large numbers of tourists gather in front of the clock to see the Apostles.

The show goes as follows:

Firstly, Death, represented by a skeleton, pulls the bell cord with one hand while holding an hourglass in the other.

Then, the Apostles come out in a procession, across the top half of the Orloj.

When they go back inside, a cockerel flaps its wings and crows and the clock chimes the hour, accompanied by a Turk shaking his head, a miser watching his bag and Vanity admiring himself in a mirror.

The clock dial is the central section of the Orloj and, as well as telling the time in ancient and modern formats, represents astronomical phenomena such as sunrises and sunsets, the position of the sun and moon, and other celestial movements.

The calendar makes up the bottom part of the Orloj, decorated with paintings representing the months of the year. (These are replicas. The original paintings, created by Josef Mánes in the 1860s, are now on display in the Muzeum hlavního města Prahy (City Museum Prague).)

There are many legends surrounding the clock, the most famous of which concerns the master clockmaker Hanuš himself.

It's said that the town councilors had his eyes burnt out with a hot poker, so he wouldn't be able to build another clock rivaling the beauty and fame of Prague's.

Master Hanuš then supposedly asked his apprentice to take him to the clock, which he deliberately damaged so badly that nobody could repair it -- those who tried either died or went mad soon after.

In reality, the clock wasn't very reliable and often didn't work, despite undergoing extensive repairs.

A further legend gives the skeleton the ability to foretell the future and says that if the clock is left damaged for a long time, hard times will result for the Czech nation.