Transylvania as originally defined in Treaty of Trianon, 27 years earlier, thus confirming the return of Northern Transylvania to Romania. From 1947 to 1989, Transylvania, along with the rest of Romania, was under a communist regime. The ethnic clashes of Târgu Mureș occurred between ethnic Romanians and Hungarians in March 1990 after the fall of the communist regime and became most notable inter-ethnic incident in the post-communist era. The Transylvanian Plateau, high, is drained by the Mureș, Someș, Criș, and Olt rivers, as well as other tributaries of the Danube. This core of historical Transylvania roughly corresponds with nine counties of
Celts in Transylvania the River Tisa is depicted in 2nd century BC pottery found at Pecica in Arad County, a prosperous trading center at the confluence of the two peoples. A classic period of Geto-Dacian La Tène culture began in the 1st century BC centered around the city of Sarmizegetusa Regia in south-western Transylvania. Dacian king Burebista defeated the Celtic Boii and Taurisci tribes between 60–59 BC. However, some archaeological finds in Dacian settlements and fortifications feature imported Celtic vessels and others made by Dacian potters imitating Celtic prototypes. These discoveries in sites from regions north and west of Transylvania show that relations