Neolithic long mortuary enclosures, Stoke Hammond, Buckinghamshire, c2011. Features below the plough soil that cause cropmarks can be man-made or natural. In this case it is both. The man-made features are two elongated, capsule shaped enclosures, a circular enclosure and a few large pits. The rest are marks in the gravel, created naturally during the Ice Age. The capsule shaped enclosures are examples of one of the oldest types of monument in Britain called Neolithic long mortuary enclosures. They are thought to be areas where dead bodies were placed before burial although there is debate within the archaeological community about what really went on in these enigmatic places!