A festive atmosphere on the streets of Frankfurt, as German Chancellor Angela Merkel poses for selfies... ...Twenty-five years after her native East Germany and West Germany officially became one, once more. (Nats) At a church service, Merkel was joined by Germany's President Joachim Gauck...(nats)...one of several events to mark the special day. But Germany's current challenges were not far from her mind. (SOUNDBITE) (German) GERMAN CHANCELLOR, ANGELA MERKEL, SAYING: "The refugee issue keeps us especially busy these days and I recall once again that Germany cannot solve the problem on its own." With some 800,000 migrants projected to arrive in Germany over the course of 2015... Merkel is calling on Europe -- and the international community -- to unite in finding a solution.