Zanzibar is the name of an archipelago in the Indian Ocean 25–50 km off the coast of East Africa, which is part of Tanzania. The archipelago consists of numerous small islands and two large ones: Unguja (the main island, sometimes informally referred to as ‘Zanzibar’), and Pemba Island. The archipelago was once the separate state of Zanzibar, which united with Tanganyika to form Tanzania (derived from the two names), and still enjoys a high degree of autonomy within the union. The capital of Zanzibar, located on the island of Unguja, is Zanzibar City. The city’s old quarter, known as Stone Town, is a World Heritage Site.