A former Royal Observer Corps underground observation post is located to the south-west of Market Rasen, in Middle Rasen parish. The posts were built during the Cold War, as part of a national system to provide civil and military authorities with essential information in the event of a nuclear attack. The posts were equipped with a variety of scientific and meteorological instruments, with their primary function being to monitor and record the position and strength of any nearby nuclear strikes, and the subsequent passage of radioactive fallout in the area. This information would be passed to regional and national headquarters of the United Kingdom Warning and Monitoring Organisation, assisting and informing the national authorities to co-ordinate any appropriate responses. This particular post is believed to have been opened in 1962. Access was through a 2ft square hatch on the surface, where an associated air vent can also be seen. 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 1991, when it was closed and locked. {1}{2}