Cropmarks of probable medieval salterns, to the south-west of Keyholme Farm, Marshchapel. The cropmarks also show a linear feature, likely to be the remains of a former boundary or watercourse, running along a roughly south-west to north-east axis, to the south of the probable salterns. Identified on aerial photographs dated to 1971, examined as part of the Lincolnshire Coastal Grazing Marsh project. {1}