Prague’s Famous
Astronomical Clock

Take a journey to the center of the Old Town Square in Prague and look up…Chances are you’ll immediately notice the Orloj, Prague’s astronomical clock, on the southern wall of the Old Town Hall.

First installed in 1410, this clock is the third-oldest astronomical clock in the world, and the oldest one still in operation. The clock is beautiful, full of history, and begging for a visit during your next trip to the Czech Republic. The face of the clock is stunning and complex. It features an astronomical dial, three hands, a solar plate, a rotating Zodiacal ring, an outer rotating ring, and several figures. A calendar plate hangs below the main face of the clock. This particular plate is a replacement from 1880; the original calendar plate is preserved in the Prague City Museum.

Key Elements of the Prague Astronomical Clock in Old Town

Astronomical Dial of the famous clock in Prague

The astronomical dial signifies the time of day and position of the moon and the sun in the sky. The dark blue circle in the center represents Earth, the upper blue portion represents the sky above the horizon, and the orange and black represent the sky below the horizon. The sun icon sits in the blue horizon area during daylight hours and sinks into the orange and black areas in the evening hours. The left side of the clock aligns with the dawn; the right side with dusk. Standard Roman numerals adorn the clock face and indicate local time in Prague on a standard 24-hour model. The outer ring of the clock is made up of golden Schwabacher numerals, which indicate Old Czech time. This ring rotates throughout the year to indicate the time of the sunset, denoted by the 24th numeral.

The Zodiacal Ring of Prague’s Astronomical Clock

The inner ring is the Zodiacal ring and showcases the 12 signs of the standard zodiac. The ring indicates which sign the sun is currently residing in on the zodiac calendar. The signs are listed anticlockwise. The sun medallion moves through this ring. You can tell the time in this ring, with the help of the sun, in three ways:

• The positioning of the hand over the Roman numerals indicates local Prague time
• The sun’s placement over the curved golden lines denotes uneven hours
• The position of the hand over the outermost ring represents the number of hours passed since sunset in Old Czech Time

The moon medallion, half silver and half black in color, also moves through this ring and indicates the lunar phases. The moon medallion moves more quickly than the sun, as it mimics the moon’s orbit of the Earth and is powered by gravity.

The clock’s interior is a complex system of gears. A 365 tooth gear operates the sun medallion, a 379 tooth gear works the moon medallion, a 57 tooth gear rotates of the moon medallion on its arm, a 366 tooth gear moves the zodiac ring, and a 24 tooth gear connects the sun and the moon medallions.

The Orloj is a beautiful and intricate machine with several wonderful and interesting elements to note. Keep reading to learn more...

The figures of “The Walk of the Apostles” on Prague’s Astronomical Clock

Four figures adorn the outside of the clock and move upon the changing of the hour. These figures symbolize vices. On the left of the clock face Vanity holds a looking glass, and next to him Greed holds bags of money. To the right of the clock face, a skeleton represents Death, next to him a Turk, representing Vice and Lust, plays the lute. Every hour, the skeleton will ring the bell, and the three other figures will shake their heads no, signifying that they are not yet ready to die. In two windows above the main clock, Jesus and the Apostles parade every hour on the hour. This feature was added in the 19th century.

The Legend and Curse of Prague’s Astronomical Clock

Four figures adorn the outside of the clock and move upon the changing of the hour. These figures symbolize vices. On the left of the clock face Vanity holds a looking glass, and next to him Greed holds bags of money. To the right of the clock face, a skeleton represents Death, next to him a Turk, representing Vice and Lust, plays the lute. Every hour, the skeleton will ring the bell, and the three other figures will shake their heads no, signifying that they are not yet ready to die. In two windows above the main clock, Jesus and the Apostles parade every hour on the hour. This feature was added in the 19th century.