Zanzibar is a semi-autonomous region of Tanzania, consisting of many islets and two large islands: Unguja and Pemba Island. Zanzibar City, located on the island of Unguja, is the capital of the archipelago and its historic center, known as Stone Town, is a World Heritage Site. Situated directly on the Indian Ocean trade routes Zanzibar has been accessible to both traders and colonists from Arabia, South Asia, and the African mainland. This was a prosperous time for Zanzibar until the beginning of Portuguese rule that in the 16th century conquered all the seaports in East Africa, including Zanzibar and the Omani capital of Muscat. In the 17th century, the Omanis expelled the Portuguese from Muscat and took control of Zanzibar, ruling until the revolution in 1964. However, in 1890 the British proclaimed a protectorate over Zanzibar reducing the sultan’s authority and restricted the slave trade. In 1963 Zanzibar was granted constitutional independence.