Stargazing: Cheomseongdae Observatory, South Korea

(pic by Greg Rakozy @ unsplash)

In the ancient world, astronomy and astrology were intertwined. For early civilisations, the stars were a source of both practical and philosophical wisdom.

In the 7th Century, the ruling powers of Ancient Korea believed, as their ancestors had, that the fates and fortunes of their kingdoms were written in the stars. It was understood that monarchs were divinely selected and political decisions were made after the careful consideration of star charts.

These intricately detailed star maps, or planispheres, were created by court astronomers. Using rudimentary tools like armillary spheres ( which look a bit like a globe made of rings), they would watch the skies and document the constellations.

In 632, when Queen Seongdeok ascended to the throne, the astronomers of ancient Korea finally received a technology upgrade.

This is it.

The 9 metre granite stone tower was named Cheomseongdae which loosely translates to ‘a place to watch the stars go by’ (or, if you prefer historical accuracy, ‘reverently regarding the stars platform’) and was constructed in the arts and science hub of Gyeongju, capital of the Silla kingdom.

The bottle-shaped tower has a small window, but no door. Historians believe astronomers weren’t intended to go inside, but instead would scale a ladder and sit on a tiny ledge at the top of the tower. From here they, possibly with the help of an armillary sphere, they would make and document their celestial observations.

(pic by Bobby Stevenson @ unsplash)

Now, at first, this doesn’t sound too different to how it was done prior to the observatory being built. However, astronomical records produced with the use of Cheomseongdae were more prolific and detailed than ever before.

So what was this secret of this seemingly low-tech tower?

Perhaps there was something about being precariously perched atop a 29 foot building that motivated the astronomers.

Or, maybe it was the fact they they could be seen by the whole city as they worked. Consequently, there was no opportunity to sneak-off for “smoko”.

“I just can’t with these stars today.”
Photo by Amir SeilSepour on

Whatever the reason for it, Cheomseongdae observatory was a tremendous success and it stands today as a monument to ancient scientific innovation and Queen Seongdeok, Korea’s first female sovereign.


According to historians Cheomseongdae is full of time-themed “Easter eggs”:

The 27 layers of granite brick which correspond to Queen Seongdeok being the 27th sovereign of Silla.

The number of bricks used in it’s construction is said to represent the amount of days in the year. (Although, scholars can’t seem to agree if there are 362, or 365…or even 366 bricks).

The square window in the tower was built with 12 layers of brick above and below, which some historians have said signify the 12 months of the year and the 12 (Chinese) zodiac signs.

Finally, the square base on which the tower is built is said to represent the four seasons.

Although, personally, I think that’s reaching.

Don’t most buildings have four sided bases?

(Pic by Nick Fewings @ unsplash)

References and further reading:

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