Many ancient cultures built structures to tell time (like sundials) or mark the passing of seasons by placing them in the direction of the sunrise on solstices or where the Sun would create a shadow on a particular day. The study of the astronomical knowledge and achievements of these prehistoric cultures is called archaeoastronomy.
One of the most famous structures built to mark seasons is Stonehenge in Wiltshire, England. Stonehenge served as a social and religious gathering place, but also as an astronomical device. Archaeologists have created reconstructions of what Stonehenge originally looked like; on the summer solstice, the Sun rises directly over the Heel Stone. In New Mexico, USA, the Pueblo People made a structure called the Sun Dagger in Chaco Canyon. On noon at the summer solstice, a single “dagger” of sunlight pierced the center of a stone spiral, while at the winter solstice, two daggers of light appeared on either side of the spiral. Unfortunately, due to a shift in the rocks, this effect no longer occurs.
Another famous example is the lines and patterns of the Nazca desert in Peru, although archaeoastronomers are unsure as to what astronomical significance they might hold. For example, many patterns are large figures of animals that may be representations of constellation, but nothing is none for sure. Other cultures, such as the Inca Empire, believed their rulers were descendants of the Sun. The World Heritage Site in Machu Picchu has different structures aligned with the sunrise on both the winter and the summer solstices.
These ancient cultures show us just how important celestial objects were and that the study of the stars is an ancient tradition going back thousands of years. While in modern times we use fancy observatories, telescopes on Earth and in space, and probes sent out into the Solar System, ancient civilizations built simple structures to study and observe phenomena created by the Sun, the Moon, and the stars.
The Cosmic Perspective: The Solar System by Bennett, Donahue, Schneider, and Voit