Towards the close of the Neolithic period, farm production rose and groups of humans identified with specific geographical areas. They also started to build large tombs or collective graves: dolmens and passage graves. Such megalithic monuments required considerable effort and co-ordinated labour to build. The dead person was placed inside the megalith together with grave goods and offerings. When the chamber was required for another deceased person, the bones were gathered and put to one side, and the new body was placed in the central position. Most megaliths were placed in significant spots by way of a landmark.