Bangui lies on the northern banks of the Ubangi River just below a series of rapids that limit major commercial shipping farther upriver, on the southern border. The navigable Ubangi River turns sharply south below Bangui and connects to the Congo River just south of the equator near Brazzaville as its chief northern tributary. The river marks the border between the Central African Republic and the Democratic Republic of the Congo (DRC). The Congolese town of Zongo sits opposite the river from Bangui.