Teaching Korea has an excellent resource pack with teaching suggestions on Cheomseongdae, the world’s oldest surviving astronomy tower.
This tower was built in the 7th century CE during the reign of Queen Seondeok of Silla (632-647).
For more about Cheomseongdae and Seondeok, check out the Teaching Korea website.
Cover image by Zsinj, shared under a CC 4.0 license on Wikimedia Commons