Fun Facts: Prague’s Astronomical Clock

Our first Friday in Prague, Remote Year organized a community breakfast at our coworking space (K1o — amazing!) and invited The Naked Tour Guide, a fellow K10 coworker, to speak.

Marcus, the Naked Tour Guide founder, told us his story of first coming to Prague from the UK on Erasmus to study history and needing to do some part-time work. A friend suggested he be a tour guide, but Marcus was not terribly impressed by the average structure or standards of the other tours. So he created his own.

Three years later, he now lives in Prague and runs The Naked Tour Guide full-time. The tours are capped at 8 people, and Marcus and the other guides have backgrounds in history, political science, and architecture. So they actually know and are passionate about the things they talk about on the tour. Imagine that!

They also have made a map of Prague that’s well-designed (featuring the clock, naturally) and includes their personal recommendation of activities and restaurants. Although I navigate with google maps, it was nice to have and we used it to find places to visit and things to eat.

The best part of our community breakfast talk, though, was during our Q&A when someone asked Marcus to give us an example of something we’d learn on the tour. So he had us pull up an image of the famous Prague Astronomical Clock and launched into a fascinating 15 minute talk.

Marcus in the K10 meeting room, telling us about the clock, and the clock in the square at night.

The Clock

The clock was built 200 years before it was proven that the earth rotated around the sun.

As a result, it’s designed with an image of the earth surrounded by four colors on the face of the clock — black, orange, green, and blue — which represent phases of the day (blue is day, orange is dusk, black is night).

The sun (the bright golden orb) moves around so that it hovers above the color that is the time of day it is — the sun goes around the earth once every 24 hours.

There are astronomical signs on the wheel behind the sun, which shows which constellation the sun is currently in. There is also a silver and black orb — the moon, with a “dark side” — which shows the cycle of the moon as well as which constellation the moon is currently in.

Telling Time

One way to tell the actual time of day is using Babylonian time, which means that it assumes 12 segments of a day. To accommodate for the shorter winter days and longer summer days, the hour segments taper in, and the sun moves around to show the hour.

The clock also shows old Czech time with numbers around to 24 (outer ring), which marked sunset — as once the sun went down, the day and workday ended. So there’s a golden hand that points to an hour, which lets you know how many hours it’s been since sunset the previous day. So, using my photo above as an example, if the hand points at 18, then it’s been 18 hours since the last sunset and is 6 hours until the next sunset. If they sun last set at 8:30 pm, then 18 hours later means it’s 2:30 pm. Cool!

Central European time is shown by the hand’s placement between the roman numerals.

The Calendar

This was added 80 years later and has 365 segments showing the Saint’s Day for every day of the year, which is celebrated similar to a birthday.

When I lived in Bulgaria, my students would come in with chocolates on their Saint’s Day and we’d all congratulate them and take a piece of chocolate. I wasn’t mad about it.

The constellations on this calendar are different sizes because they’ve been evened out to 30 days each whereas the actual duration of time the sun is in each constellation varies. Oh no — our horoscopes may not be right after all!!!!!!

The Statues

The bottom four statues are the positive things in society, from the 1600s: a philosopher with a scroll, archangel Micheal with a sword, an astronomer with a telescope, and a chronicler/historian with a book.

Above them are the four 17th century threats to Prague: Vanity with a mirror, Greed with money, Death with an hourglass and holding a rope to ring the bell the clock tower, and the Turk with a musical instrument. Greed was formerly known as The Jew and had a beard, but after the Holocaust, they took off the beard and rebranded him, so to speak, whereas the Turk remains as such — an interesting note of history and attitudes.

On every hour, each of the four threats move a bit and the wooden doors above the clock open to show the 12 apostles rotating through. When the doors close, they force air up to make the rooster flap his wings and crow, which symbolizes the Gospel narrative of the three denials of Christ. This was meant to remind people of the importance of telling the truth.


Wasn’t that fascinating? It’s much better to hear Marcus tell it firsthand, so you should probably book a tour with them if you ever go to Prague. (And no, I’m not being paid to say any of this.)

I went on the Prague Night Tour with Marcus, and found it very interesting — both because of the history and information he shared and to see the Prague Castle at sunset and night. As an Art History nerd, I appreciated what he knew about the castle’s art and architecture.

He even described flying buttresses as best as I’ve ever heard: imagine it’s like a stage set — you’re just trying to prop it up and create a facade without showing how it works.

So inside the church, they were trying to create this experience of beautiful open space and huge windows flooding the room with the colorful light of God. To do that — to build big stone walls with huge windows AND create a large space in the middle, you have to prop everything up from behind and keep away from the windows. Voila, flying buttresses.

After the tour, we went to a local pub, I tried unfiltered beer on his recommendation, and we tapped into his ability to answer pretty much any European history question off the top of his head.

All in all, the tour and the breakfast talk were definitely two of the touristy learning highlights of my month in Prague.


Katherine is a digital nomad, working remotely while she travels the world — on the road since June 2014. She’s a member of Remote Year 2 Battuta, living around the world with 75 other digital nomads from February 2016 to January 2017.

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