Thanks to the astronomical clock, it was possible from that time on in a multicultural city, which Prague undoubtedly was, to read the time using an alternate method. With the unveiling of the astronomical clock, Prague took its place among such Medieval metropolises as Padua, Bern and Strasbourg.

The astronomical clock has been improved and repaired several times throughout its existence, as it has certainly been through its fair share of hardships. In the 18th century it was nearly lost forever to the scrap heap, while the most recent great misfortune came at the very end of the Second World War when the Old Town Hall was bombed out.

It was, nevertheless, successfully repaired in the end. With about three quarters of the old original parts, it is still functional and is thus the most well preserved of its kind across the globe.

What exactly does the clock display?

The clock’s key component is its astrolabe, an astronomical instrument with the help of which astrologers and mariners since the Middle Ages have determined the positions of the stars, the Sun and the Moon. It also served for determining local time as well as for navigation.

The astrolabe comprises a large brass ring consisting of two circular components joined in the middle by a peg. By setting the relative positions of these circular components, it is possible to depict the position of the stars in the sky. The Tropic of Capricorn and the Tropic of Cancer are represented on the astrolabe by circles, though the equator is not marked. The signs of the zodiac can be seen around the astrolabe’s perimeter. 

On the outer ring of the clock, golden numerals indicate Old Czech Time (or Italian time), according to which the day began at sunset. Central European Time (or Old German Time) is indicated by the golden hand. Essentially, this is the time by which we order our day, though the clock did not sound the time until after the post-war reconstruction of 1948.

A unique feature of the Old Town astronomical clock is that it shows Babylonian time, which was calculated from sunrise to sunset and thus the duration of hours changed with the seasons, i.e. longer in summer than in winter. The Prague Orloj is the only one in the world that measures this time.

The lower part of the clock features a calendar dial which shows the day and its place in the week as well as the month and year. Two hands of the clock deserve particular attention. One, with an icon of the Moon, shows the phase of the Moon (i.e. its waxing and waning).

The second, with an icon of the Sun, is the most important part of the clock as the astrolabe is adjusted according to local solar time. The Sun is located on the same arm as the golden hand indicating the time.

Let’s not forget the Apostles

Another feature of the Prague Orloj is the procession of the Apostles. At the top of every hour from 9 a.m. to 9 p.m., the Apostles appear in the clock’s upper windows with their special attributes in hand. The procession was fabricated by the sculptor and woodcarver Vojtěch Sucharda – twice!

The first time in 1912, and again after the clock was damaged by fire at the end of the Second World War. A small figure of a rooster, symbolising life, is placed above these windows. Its crow always concludes the parade of the Apostles. Flanking the clock, you can see four animated figures. On the left side, Vanity is represented by the figure holding a mirror.

The wooden statue nods its head while admiring himself in the mirror. The Miser holds in his hands a cane and a purse which he waves while shaking his head disapprovingly. Both figures were destroyed during WWII and were replaced with copies from the mid-20th century. The figure of Death, or the Skeleton, survived the Old Town Hall fire and has been part of the clock since the 15th century.

The Skeleton turns an hourglass with which it counts down human life, thereby reminding us with its chime and concurrent oscillation of our inevitable fate. The figure of the Turk is depicted with a lute and symbolises profligacy and lust as human vices. The clock also bears statues of Michael the Archangel, a Philosopher, an Astronomer and a Chronicler.