A cairn is a human-made pile or stack of stones, often used as a trail marker or a memorial. These structures can vary in size and shape, and they are commonly found in mountainous or remote areas. Cairns serve as navigational aids for hikers and can also signify important locations, such as summits or burial sites. Historically, cairns have been used by various cultures around the world, including the Inuit in North America and the Celts in Europe. They can hold cultural significance, representing respect for the deceased or marking significant events. Today, cairns continue to be a practical tool for outdoor enthusiasts.