Zanzibar, Swahili Unguja, island in the Indian Ocean, lying 22 miles off the coast of east-central Africa. In 1964 Zanzibar, together with Pemba Island and some other smaller islands, joined with Tanganyika on the mainland to form the United Republic of Tanzania. The general impression of Zanzibar when approached from the mainland is of a long, low island with small ridges along its central north–south axis. Coconut palms and other vegetation cover the land surface. It is 53 miles at its greatest length and 24 miles broad. The highest point of the central ridge system is Masingini, 390 feet above sea level. Higher ground is gently undulating and gives rise to a few small rivers, which flow west to the sea or disappear in the coral country..