Carved stone balls are petrospheres dated from the late Neolithic, to possibly as late as the Iron Age, mainly found in Scotland, but also elsewhere in Britain and Ireland. They are usually round and rarely oval, and of fairly uniform size at around inches or 7 cm across, with anything between 3 and 160 protruding knobs on the surface. They range from having no ornamentation (apart from the knobs) to extensive and highly varied engraved patterns. A wide range of theories has been produced to explain their use or significance, with none gaining very wide acceptance. They are not to be confused with the much larger smooth round stone spheres of Costa Rica. Age and distribution Carved stone balls date as old as 5,200 years old, coming from the late Neolithic to at least the Bronze Age. Nearly all have been found in north-east Scotland, the majority in Aberdeenshire, the fertile land lying to the east of the Grampian Mountains. A similar distribution to that of Pictish symbols led to the early suggestion that carved stone balls are Pictish artefacts. The core distribution also reflects that of the Recumbent stone circles. As objects they are very easy to transport and a few have been found on Iona, Skye, Harris, Uist, Lewis, Arran, Hawick, Wigtownshire and fifteen from Orkney. Outside Scotland examples have been found in Ireland at Ballymena, in England at Durham, Cumbria, Lowick, and Bridlington. A single example was found in Norway in a medieval cairn. Recent theory is that the Norway example was carried home by a Viking from an expedition to Scotland. The larger (90mm diameter) balls are all from Aberdeenshire, bar one from Newburgh in Fife. By the late 1970s, a total of 387 had been recorded. Of these, by far the greatest concentration (169) was found in Aberdeenshire. By 1983 the number had risen to 411 and by 2015 over 425 balls had been recorded. A collection of over 30 carved balls from Scotland, Ireland and northern England is held by the British Museum. Archaeological context Many of the balls have not had their discovery site recorded and most are found as a result of agricultural activity. Five were found at the Neolithic settlement of Skara Brae and one at the Dunadd hillfort. The distribution of the balls is similar to that of mace-heads, which were both weapons and prestige objects used in ceremonial situations.