Tanzania: The Swahili city of Kilwa, on the Tanzanian coast. From Civitates Orbis Terrarum (1572).

In the 11th century, the island of Kilwa Kisiwani was sold to a Persian trader Ali bin Al-Hasan, who founded the city and the Kilwa Sultanate. Over the next few centuries, Kilwa grew to be a major city and trading centre along that coast, and also inland as far as Zimbabwe. Trade was mainly in gold and iron from Zimbabwe, ivory from Tanzania, and textiles, jewelry, porcelain, and spices from Asia. By the 12th century, under the rule of the Mahdali, Kilwa had become the most powerful city on the East African coast. At the zenith of its power in the 15th C., the Kilwa Sultanate owned or claimed overlordship over the city-states of Malindi, Mombassa, Pemba, Zanzibar, Mafia, Comoro, Mozambique, Sofala, and the trading posts across the channel on Madagascar. Abu Abdullah Ibn Battuta recorded his visit to the city around 1330, and commented favorably on the humility and religion of its ruler, Sultan al-Hasan ibn Sulaiman. From this period date the construction of the Palace of Husuni Kubwa and a significant extension to the Great Mosque of Kilwa. In the early 16th century, Vasco da Gama extorted tribute from the wealthy Islamic state, and soon after, another Portuguese force commanded by D. Francisco de Almeida took control of the island in 1505. It remained in Portuguese hands until 1512, when an Arab mercenary captured Kilwa. The city regained some of its earlier prosperity, but in 1784 it came under the rule of the Omani rulers of Zanzibar. After the Omani conquest, the French built and manned a fort at the northern tip of the island, but the city itself was abandoned in the 1840s. It was later part of German East Africa from 1886 to 1918. Serious archeological investigation began in the 1950s. In 1981 it was declared a UNESCO World Heritage Site, and noted visitor sites are the Great Mosque, the Mkutini Palace and some remarkable ruins. (Photo by: Pictures From History/Universal Images Group via Getty Images)