Land History Samples of stone arrangements from different map units are shown below. Map unit “Pioneering Stage” (PURPLE): generally simple stacks of local stones associated with stone piles. Map unit “Established Farm Stage” (GREEN); Some walls are carefully laid, and stone is much more concentrated. Map unit “Forest and City Stage” (YELLOW): generally complex variablity, from ancient tumbled walls to estate architecture in yellow areas. Link back to stone wall provinces.