A terrain of lines
The Carnac Alignments are the largest collection of megalithic monuments in the world. More than 3,000 prehistoric standing stones, hewn from local granite, stretch across the landscape for nearly 4 kilometers. The complex consists of multiple types of structures, including stone rows (alignments), stone tombs (dolmens), and burial mounds (tumuli). The construction took place during the Neolithic period, with most activity occurring between 4500 BCE and 3300 BCE. The oldest structures at Carnac more than a millennium older than the sarsen stones of Stonehenge.
The alignments are organized into three main groups: Ménec, Kermario, and Kerlescan. Le Ménec is the largest, with 1,099 menhirs arranged in eleven converging rows that are 1,165 meters long. The stones follow a pattern: the tallest, around 4 meters high, stand at the western end, shrinking in the middle before rising again at the eastern end. The Kermario alignment features 1,029 stones in ten rows over a distance of about 1,300 meters. The Kerlescan group is smaller, with 555 stones in 13 lines, ending in the west with a circle of 39 stones. These groups may have once formed a single, massive alignment that was later broken up as stones were removed for other building projects.
An unsolved purpose
The function of the Carnac Alignments remains unknown, as the pre-Celtic people who built them left no written records. Scientific investigation points to several possibilities. One theory is archaeoastronomical. In the 1970s, Scottish engineer Alexander Thom surveyed the site and proposed that the alignments and nearby individual menhirs functioned as a complex lunar observatory. He suggested that sightlines between specific stones marked the extreme positions of the moon's rising and setting. The Crucuno stone rectangle, a formation of 21 menhirs nearby, forms a perfect 3-4-5 Pythagorean triangle with its diagonal aligned to the midsummer sunrise.
Other theories propose the rows were processional avenues for religious ceremonies or as territorial markers between different Neolithic groups. The sheer scale of the project indicates a high degree of social organization over many generations. The stones themselves are local Hercynian granite, and their quarrying and transport was a massive project. Today, the sites are protected. Fences were erected in 1991 to prevent erosion from visitors, which was causing the ancient stones to destabilize and fall.