It borders the Central African Republic and South Sudan to the north; Uganda, Rwanda, and Burundi in the east; Zambia and the Portuguese overseas province of Angola to the south; the Central African Republic, the Portuguese overseas province of Portuguese Congo, and the Atlantic Ocean to the west; and is separated from Tanzania by Lake Tanganyika in the east. The country has access to the ocean through a 40 km (25 mi) stretch of Atlantic coastline at Muanda and the roughly nine km wide mouth of the Congo River which opens into the Gulf of Guinea. It has the second-highest total Christian population in Africa.