For thousands of years, ancient societies all around the world erected massive stone circles, aligning them with the sun and stars to mark the seasons. These early calendars foretold the coming of spring, summer, fall and winter, helping civilizations track when to plant and harvest crops. They also served as ceremonial sites, both for celebration and sacrifice.
These megaliths — large, prehistoric monuments made of stone — may seem mysterious in our modern era, when many people lack a connection with, or even view of, the stars. Some even hold them up as supernatural, or divined by aliens. But many ancient societies kept time by tracking which constellations rose at sunset, like reading a giant, celestial clock. And others pinpointed the sun’s location in the sky on the summer and winter solstice, the longest and shortest days of the year, or the spring and fall equinox.
Europe alone holds some 35,000 megaliths, including many astronomically-aligned stone circles, as well as tombs (or cromlechs) and other standing stones. These structures were mostly built between 6,500 and 4,500 years ago, largely along the Atlantic and Mediterranean coasts.
The most famous of these sites is Stonehenge, a monument in England that’s thought to be around 5,000 years old. Though still old, at that age, Stonehenge may have been one of the youngest such stone structures to be built in Europe.
The chronology and extreme similarities between these widespread European sites leads some researchers to think the regional tradition of constructing megaliths first emerged along the coast of France. It was then passed across the region, eventually reaching Great Britain.
