Once Catholic then Lutheran. Black because there was a massive fire and the insides were blackened. Few things survived but one was a painting of Mary to whom the church is dedicated and miraculously her face remained white. Thus she is the Black Madonna. Big was important in the day - church can protect 5000 but the population was only 2000 when it was built. More to keep the Ottoman Turks in their rightful place (ie not in Transylvania)