Pope Francis, left, arrives with Ecumenical Patriarch Bartholomew I to attend an ecumenical prayer at the Patriarchal Church of St. George in Istanbul, Saturday, Nov. 29, 2014. The two major branches of Christianity represented by Bartholomew and Francis split in 1054 over differences on the power of the papacy. The two spiritual heads will participate in an ecumenical liturgy and sign a joint declaration in the ongoing attempt to reunite the churches. (AP Photo/Gregorio Borgia), APTOPIX