The CHEOMSEONGDAE OBSERVATORY (Gyeongju, S. Korea)
National Treasure No. 31
A place that raises more questions than provides answers. Our hosts were full of speculation and conjecture. What exactly was this structure? Why and how was it built?
This astronomical observatory tower was built in the reign of Queen Seondeok (reigned 632-647), who was the 27th ruler of the Silla Dynasty in Korea, and is thought to be the oldest existing observatory in the East. This telescope-shaped structure was probably used by a number of generations of Silla astrological diviners. It is 9.4 meters high and 5.17 meters in diameter, and the length of the stone base is 5.35 meters. Up to the 12th layer from the bottom, this hollow tower was filled with sand and pebbles. Between the 13th and the 15th layer, there is a square opening through which an observer can ascend to the top.
Astronomers today question how the tower was actually used. Note certain intriguing facts in the apparently simple design that might help to explain: the construction used 365 stones, the number of days in a calendar year; there are 12 rectangular base-stones and 12 separate levels of stones above and below a central window/door. Does this number 12 imply the zodiac or the number of months in a year? The length of the top stone is just half that of the base stone, and squared and circular shapes are carefully arranged, symbolizing a round sky and square ground. Other technical details relate to the tower’s position in relation to certain stars.
Compared to the huge burial mounds close by, this is a small structure, but its attraction is large. We visited on a rainy day and the wet stones seemed to add to the air of mystery.