The Bedfordshire Historic Environment Record [HER] contains information on the county’s historic buildings and landscapes and summaries of each entry can now be found online as part of the Heritage Gateway website. Cropmarks occur when crops grow at different rates due to walls, ditches and other features beneath them affecting the rate of growth. There are two cropmarks which are thought to be prehistoric in Ion.
There is a small, "sub-square" cropmark north-east of Ion Lodge [HER 16759]. East of Ion Lodge is small group of joined "sub-rectangular" enclosures [HER 16816].