Overview Unguja, also known as Zanzibar Island, is the main island in the Tanzanian archipelago of Zanzibar. Stone Town, part of Zanzibar City, is an old trade center, with mosques and winding lanes. The 1883 House of Wonders is a former sultan’s palace with a clock tower. The Old Fort now houses a cultural center and a stone amphitheater. Underground aqueducts fed hot water to the late-19th-century Hamamni Persian Baths.