Celtic field is an old name for traces of early (prehistoric) agricultural field systems found in North-West Europe, i.e. Britain, Ireland, Belgium, Netherlands, Germany, Denmark, France, Sweden, Poland and the Baltic states. The fields themselves are not related to the Celtic culture. The name was given by O.G.S. Crawford. They are sometimes preserved in areas where industrial farming has not been adopted and can date from any time from the Early Bronze Age (c. 1800 BC) until the early medieval period. They can be preserved as earthworks or soil marks.