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
Transylvania Catholic, Lutheran, Reformed, and Unitarian branches. Other faiths also are present, including Jews and Muslims. Under the Habsburgs, Transylvania served as a place for "religious undesirables". People who arrived in Transylvania included those that did not conform to the Catholic Church and were sent here forcibly, as well as many religious refugees. Transylvania has a long history of religious tolerance. This has been ensured by its religious pluralism. Christianity is the largest religion in Transylvania. Transylvania has also been (and still is) a center for Christian denominations other than Eastern Orthodoxy, the form of Christianity that most Romanians follow. As