Celts in Transylvania arrived in northwestern Transylvania in around 400–350 BC as part of their great migration eastwards. When Celtic warriors first penetrated these territories, the group seem to have merged with the domestic population of early Dacians and assimilated many Hallstatt cultural traditions. The second half of the 4th century BC saw the Middle La Tène Celtic culture emerge in north-western and central Dacia, a development reflected especially in burials of the period. Celtic artifacts dating to this time have been discovered at Turdaş, Haţeg and Mediaş in modern-day Romania. By 1976, the number of Celtic sites found in Transylvania had reached
Transylvania withdrew in 271 AD, it was overrun by a succession of various tribes, bringing it under the control of the Carpi, Visigoths, Huns, Gepids, Avars and Slavs. From 9th to 11th century Bulgarians ruled Transylvania. It is a subject of dispute whether elements of the mixed Daco–Roman population survived in Transylvania through the Post-classical Era (becoming the ancestors of modern Romanians) or the first Vlachs/Romanians appeared in the area in the 13th century after a northward migration from the Balkan Peninsula. There is an ongoing scholarly debate over the ethnicity of Transylvania's population before the Hungarian conquest (see Origin of