Wood decays and any earthen feature has since been eroded by centuries of ploughing.
They are known as cropmarks.
Cropmarks at Grezac, France.
Crops growing above long-gone ditches will grow taller, thicker and greener on account of more nourishment.
How crop marks form?
An ancient settlement with fortification or drainage ditch around it.
Graphics by: RCAHMW
Over the centuries the settlement disappeared and farming took place.
Graphics by: RCAHMW
The ditches got filled in and the soil became deeper in those areas.
During intense dry spells crops in the deeper ditches survive because those areas hold more water and nutrients.
According toBBC, no plans are being made to dig on the site, which is a working farm.
And once the crop is harvested, the image will disappear.
Meanwhile, in Clumber Park in Nottinghamshire, the outline of an 18th century estate has appeared.
In Gawthorpe Hall, Lancashire, the dry weather has brought back a Victorian garden.
The almost ploughed-down medieval castle mound at Castell Llwyn Gwinau, Tregaron, showing clearly under parched conditions.
Photo credit: RCAHMW
Newly discovered crop marks of a prehistoric or Roman farm near Langstone, Newport.
Photo credit: RCAHMW
Extensive crop marks of Trewen Roman farmstead or villa, Caerwent, Monmouthshire.
