Menhirs are large upright stones that were often erected in prehistoric times. They can be found in various parts of the world, particularly in Europe, and are believed to have served various purposes, such as marking territory, commemorating events, or serving as religious sites. The stones vary in size and shape, and many are made from local materials. These ancient structures are often associated with megalithic cultures, which constructed large stone monuments. Menhirs can be found alone or in groups, sometimes forming alignments or circles, and they are often linked to other structures like dolmens and stone circles.