 Complete the following phrase:  The history of pre-Celtic Europe and Celtic origins are debated. According to one theory, the proto-Celtic language arose in the Late Bronze Age Urnfield culture of central Europe, which flourished from around 1200 BC. This theory links the Celts with the Iron Age Hallstatt culture which followed it c. 800450 BC, named for the rich grave finds in Hallstatt, Austria. Therefore, this area of central Europe is sometimes called the Celtic homeland. It proposes that by the following La Tène cultural period c. 450 BC onward, named after the La Tène site in Switzerland, Celtic culture had spread westward by diffusion or migration to France and the Low Countries Gauls, the British Isles Insular Celts, the Iberian Peninsula Celtiberians, Gallaecians, Celtici and northern Italy Lepontii and Cisalpine Gauls. Another theory suggests that proto-Celtic arose earlier in the Atlantic Bronze Age coastal area and spread eastward. Following the 