A number of truly ancient sites such as Stonehenge, the Goseck circle, or any number of primitive European circles and henges, have orientations and architectural features that correspond with solstices. How would an ancient people have determined which of these days were the shortest/longest without an ability to time sunrises and sunsets or accurate astronomical measurement equipment?
You can determine the solstices with nothing more than a stick if you know how. In the northern hemisphere the summer solstice is the point where the sun is at its highest elevation from the southern horizon. The winter is correspondingly the point when the sun is at its annual lowest. The cardinal directions can also be derived from the movement of the sun in temperate latitudes.
What this means is that if you watch the shadows cast by the stick, they'll move between two points that correspond to the solstices. In certain regions (including Arizona), the stick used was actually a mountain, sometimes with a hole in it. In other regions like Britain, the large post-holes in ritual complexes may have held the poles used in ritual astronomy. In all cases, more elaborate structures like Stonehenge were almost certainly developed from simpler astronomical tools and knowledge.