Across Western Europe, the Early Neolithic marked the first period in which humans built monumental structures in the landscape. These structures included chambered long barrows: rectangular or oval earthen tumuli that had a chamber built into one end. Some of these chambers were constructed out of timber, while others were built using large stones, now known as "megaliths". These long barrows often served as tombs, housing the physical remains of the dead within their chamber. Individuals were rarely buried alone in the Early Neolithic, instead being interred in collective burials with other members of their community. These chambered tombs were built all along the Western European seaboard during the Early Neolithic, from southeastern Spain up to southern Sweden, including most of the British Isles; the architectural tradition was introduced to Britain from continental Europe in the first half of the fourth millennium BCE. While there are stone buildings—like Göbekli Tepe in modern Turkey—which predate them, the chambered long barrows constitute humanity's first widespread tradition of construction using stone.