One of the more interesting ways to determine how old a culture is, is if they have a solar observatory. Such an observatory needs only three markers. The equinox marker in the middle, and the two solstice markers on either side of it.
The distance between these three matter, because the axis tilt of the Earth is considerably less than it used to be. This long-term shift is known as "the precession of the equinoxes." This change isn't measured in relation to the sun, but rather to the other stars in the sky. Every 26,000 years the Earth's axis goes through a cycle of pointing to different parts of the sky.
Concurrently, on Earth it seems that the yearly axis shift becomes less and less.
In human terms, this would mean that the two solstice points will have moved closer together in our present day, and knowing how much shift happens every year, we can tell when the observatory was originally built.
Thanks, good info...I never would have thought of that.