Passage graves are ancient burial structures found primarily in Ireland, Scotland, and Scandinavia. They typically consist of a long passage leading to a central chamber, where human remains and grave goods were placed. These structures are often made of large stones and are covered with earth, forming a mound. The design of passage graves reflects the architectural skills of prehistoric communities. They are believed to have been used for communal burials and may have held religious or ceremonial significance. Notable examples include Newgrange in Ireland and Maeshowe in Orkney.