Importantly, Earth’s axial tilt works in about a 42,000 year cycle, and we are on the declining side of the cycle, at about 23.4°.
The Earth’s axial tilt varies in this cycle between 22.1° and 24.5°. While this doesn’t seem like much, 10,000 years ago, it would have meant less glaciation at the poles, and considerable difference in the seasons.
On the ground, a simple solar observatory just needs four points. The point of observation, two markers to indicate the solstices, and one in the middle to indicate the equinox. It can be pointed to either the sunrise or the sunset.
10,000 years ago, the solstice points would have been much further spaced.