What do St. Patrick's Day, the shamrock, and the Celtic knot have in common? They all represent symbols of Ireland's rich culture. The Celts began to build their own civilization many centuries ago. They represented a collection of tribes from central Europe that shared religious beliefs, a common language, cultures, and traditions. The Celtic culture began to evolve as early as 1200 B.C. and spread throughout western Europe, with many of their legacies becoming most prominent in Ireland and Great Britain.