The Neolithic era, (3900-1700 BC) saw the start of cattle farming spreading inland from the coastal settlements. Flint axes were used, and trading occurred in flint, gold, copper and bronze. This era saw the start of barrow building for the dead, and settlements have been found at Rødkilde. Barrows became larger, longer and contained multiple burials. More than 100 large graves have been found on Møn. The period from 2400–1700 is known as Doltktiden, after the flint daggers which became common at that time. Bronze was also in use, imported from the south.