The Kreisgrabenanlage Goseck was built about 6900 years ago for use as a solar observatory. The plant is considered the oldest known of its kind worldwide. The people observed the time of the solstice at different seasons by means of the vacancies between the trunks.
The solar observatory does not look spectacular, these many piles set up in two circles. But if you realize that this was built just under 7,000 years ago and how much knowledge was already necessary, you just have to be amazed. This is a place to just pause and let it all work for you.