A former Royal Observer Corps underground observation post was located to the south-west of Crowland. The post is believed to have been opened in 1962. Access was through a 2ft square hatch on the surface, where an associated air vent would have been visible. A ladder would lead down the concrete shaft to two rooms; the first being quite small and used to house the chemical toilet. The second, much larger monitoring room measured approximately 15' by 7'6'', and would have been staffed by three observers. The post remained in use until 1968, when it was closed and demolished at some point afterwards. {1} The above-ground elements of the post can be discerned on an aerial photograph taken of this area in May 1972, showing it was still extant at this point. The post was located within a small enclosure at the corner of a larger arable field, to the immediate east of Plank Drove. {2}