The sun cross, a cross inside a circle, is one of the oldest and most widespread of symbols. The Neolithic symbol combining cross and circle is the simplest conceivable representation of the union of opposed polarities in the Western world. It often stood for the sun and the tree of life. Crossed circles scratched on stones have been recovered from Paleolithic cave sites in the Pyrenees. At the Callanish Stones in the Outer Hebrides, the most famousmegalithic site in Scotland, crossing avenues of standing stones extend from a circle. Scratched into stone or painted on pottery, as on that of the Samara culture, the crossed-circle symbol appears in such diverse areas as the Pyrenees in Old Europe, the Anatolia, Mesopotamia, the Iranian plateau, and the cities of Mohenjo-daro and Harappa in the Indus River valley. It may be compared to the yin-yang symbol of the Eastern world.
In the prehistoric religion of Bronze Age Europe, crosses in circles appear frequently on artifacts identified as cult items, for example the “miniature standard” with an amber inlay that shows a cross shape when held against the light, dating to the Nordic Bronze Age, kept in the National Museum of Denmark, Copenhagen. The Bronze Age symbol has also been connected with the spoked chariot wheel, which at the time was four-spoked (compare theLinear B ideogram 243 “wheel” 𐃏), a technological innovation that reached Europe in the mid 2nd millennium BC, and which in the context of the Sun chariot may also have had a “solar” connotation.