The cropmark traces of a possible incomplete double ditched curvilinear enclosure of uncertain date seen within the school playing field on the northern edge of Grain village. The enclosure appears as the fragmented remains of two concentric ditches of 14m and 25m in diameter. The ditches have the appearance of being causewayed, but this may be due to the poor nature of the cropmark. The western third of the site is obscured by the school buildings. This may be the remains of a Bronze Age round barrow, but there are traces of possible WW1/WW2 structures also visible as cropmarks within the playing field so it is possible that the curvilinear enclosure is of a similar date and origin. This site was mapped from aerial photographs taken by English Heritage in August 2011 as part of the English Heritage: Hoo Peninsula Landscape Project.