Used for measuring the position of celestial objects. I can't believe they needed a lotus-shaped structure to do that. Incidentally, this was the most distant of three pictures Anca took of me. I chose it, not only because you can see the whole structure, but because you can't see that I look about 8yo - identical almost to a picture that was taken when I was on holiday in Greece at the age of 15. I looked 8yo then too.