Located entirely within the tropical zone of Central Africa, the Central African Republic has an area of 622,984 sq km (240,535 sq mi), extending 1,437 km (893 mi) E – W and 772 km (480 mi) N – S . Comparatively, the area occupied by Central African Republic is slightly smaller than the state of Texas. Entirely landlocked, it is bordered on the north by Chad, on the east by Sudan, on the south by the Democratic Republic of Congo (DROC—the former Zaire) and the Republic of the Congo (ROC), and on the west by Cameroon, with a total boundary length of 5,203 km (3,233 mi). The Oubangui and Mbomou rivers form much of the southern border; the eastern border coincides with the divide between the watersheds of the Nile and the Zaire rivers. The Central African Republic capital city, Bangui, is located in the southwestern part of the country.