The incomplete cropmark of a possible Iron Age or Roman enclosure can be seen on aerial photographs taken in 2011. The cropmark of this rectilinear enclosure is situated on the southern edge of part of Gravesend known as Riverview Park. The northern part of this feature is obscured by houses on Vigilant Way. The cropmark defined an area 30m by 38m. The cropmarks of boundary ditches are also visible. Those to the west may be contemporary while others overlie or are overlain by the enclosure. These features were mapped from aerial photographs as part of the English Heritage: Hoo Peninsula Landscape Project.