Looking down the furrow of a ridge and furrow field between Market Harborough and Marston Trussell, in Northamptonshire, England.
From Wikipedia (http://en.wikipedia.org/wiki/Ridge_and_furrow):
Ridge and furrow is an archaeological pattern of ridges and troughs created by a system of ploughing used in Europe during the Middle Ages. The earliest examples date to the immediate post-Roman period and the system was used until the 17th century in some areas. Ridge and furrow topography is found in Great Britain, Ireland and elsewhere in Europe. The surviving ridges are parallel, ranging from 3 to 22 yards (3 to 20 m) apart and up to 24 inches (61 cm) tall – they were much taller when in use. Older examples are often curved.
Ridge and furrow topography was a result of ploughing with non-reversible ploughs on the same strip of land each year. It is visible on land that was ploughed in the Middle Ages, but which has not been ploughed since then. No actively ploughed ridge and furrow survives.
Straightened in ACR