Angela Merkel leads ceremonies to mark 20 years since collapse of Berlin Wall . The ceremony was attended by German President Joachim Gauck, who said the wall had been a symbol for freedom and democracy in Europe. Merkel says Germany still has far to go in its unification process .
Angela Merkel leads ceremonies to mark 20 years since collapse of Berlin Wall . Thousands of people converged on symbolic Brandenburg Gate in center of Berlin . Merkel says Germany still has far to go in its unification process .