Kilwa Kisiwani: Medieval Trade Center of Eastern Africa

Medieval Trade Center of Eastern Africa

The magnificent ruins of the Great Mosque at Kilwa Kisiwani
The magnificent ruins of the Great Mosque at Kilwa Kisiwani which was first built in the 10th and 11th centuries with important additions in the 14th century. By the 16th century, it had become the largest mosque south of the Sahara. | Location: Southeast Tanzania Tanzania. Nigel Pavitt / Getty Images

Kilwa Kisiwani (also known as Kilwa or Quiloa in Portuguese) is the best known of about 35 medieval trading communities located along the Swahili Coast of Africa. Kilwa lies on an island off the coast of Tanzania and north of Madagascar, and archaeological and historical evidence shows that together the sites conducted an active trade between interior Africa and the Indian Ocean during the 11th through 16th centuries AD.

In its heyday, Kilwa was one of the principal ports of trade on the Indian Ocean, trading gold, ivory, iron, and slaves from interior Africa including Mwene Mutabe south of the Zambezi River. Imported goods included cloth and jewelry from India; and porcelain and glass beads from China. The archaeological excavations at Kilwa recovered the most Chinese goods of any Swahili town, including a profusion of Chinese coins. The first gold coins struck south of the Sahara after the decline at Aksum were minted at Kilwa, presumably for facilitating international trade. One of them was found at the Mwene Mutabe site of Great Zimbabwe.

Kilwa History

The earliest substantial occupation at Kilwa Kisiwani dates to the 7th/8th centuries AD when the town was made up of rectangular wooden or wattle and daub dwellings and small iron smelting operations. Imported wares from the Mediterranean were identified among the archaeological levels dated to this period, indicating that Kilwa was already tied into the international trade at this time.

Historical documents such as the Kilwa Chronicle report that the city began to thrive under the founding Shirazi dynasty of sultans.

Growth of Kilwa

Kilwa became a large center as early as 1000 AD, when the earliest stone structures were built, covering perhaps as much as 1 square kilometer (about 247 acres). The first substantial building at Kilwa was the Great Mosque, built in the 11th century from coral quarried off the coast, and later greatly expanded. More monumental structures followed into the fourteenth century including the Palace of Husuni Kubwa. Kilwa became a major trade center from the 1100s to the early 1500s, rising to its first importance under the rule of the Shirazi sultan Ali ibn al-Hasan.

About 1300, the Mahdali dynasty took over control of Kilwa, and a building program reached its peak in the 1320s during the reign of Al-Hassan ibn Sulaiman.

Building Construction

The constructions built at Kilwa beginning in the 11th century AD were masterpieces constructed of coral mortared with lime. These buildings included stone houses, mosques, palaces, and causeways. Many of these buildings still stand, a testament to their architectural soundness, including the Great Mosque (11th century), the Palace of Husuni Kubwa and the adjacent enclosure known as the Husuni Ndogo, both dated to the early 14th century.

The basic block work of these buildings was made of fossil coral limestone; for more intricate work, the architects carved and shaped porites, a fine-grained coral cut from the living reef. Ground and burnt limestone, living corals, or mollusk shell were mixed with water to be used as whitewash or white pigment; or combined with sand or earth is a mortar.

The lime was burned in pits using mangrove wood until it produced calcined lumps, then processed into damp putty and left to ripen for six months, letting the rain and groundwater dissolve residual salts. Lime from the pits was likely also part of the trade system: Kilwa island has an abundance of marine resources, particularly reef coral.

Layout of the Town

Visitors today at Kilwa Kisiwani find that the town includes two distinct and separate areas: a cluster of tombs and monuments including the Great Mosque on the northeast part of the island, and an urban area with coral-built domestic structures, including the House of the Mosque and the House of the Portico on the northern part. Also in the urban area are several cemetery areas, and the Gereza, a fortress built by the Portuguese in 1505.

Geophysical survey conducted in 2012 reveals that what appears to be an empty space between the two areas was at one time filled with other structures, including domestic and monumental structures. The foundation and building stones of those monuments were likely used to enhance the monuments that are visible today.


As early as the 11th century, an extensive causeway system was constructed in the Kilwa archipelago to support the shipping trade. The causeways primarily act as a warning to sailors, marking the highest crest of the reef. They were and are also used as walkways allowing fishermen, shell-gatherers, and lime-makers to safely cross the lagoon to the reef flat. The sea-bed at the reef crest harbors moray eels, cone shells, sea urchins, and sharp reef coral.

The causeways lie approximately perpendicular to the shoreline and are built of uncemented reef coral, varying in length up to 200 meters (650 feet) and in width between 7-12 m (23-40 ft). Landward causeways taper out and end in a rounded shape; seaward ones widen into a circular platform. Mangroves commonly grow along their margins ​and act as a navigational aid when the high tide covers the causeways.

East African vessels that made the way successfully across the reefs had shallow drafts (.6 m or 2 ft) and sewn hulls, making them more pliant and able to cross reefs, ride ashore in heavy surf, and withstand the shock of landing on the east coast sandy beaches.

Kilwa and Ibn Battuta

The famous Moroccan trader Ibn Battuta visited Kilwa in 1331 during the Mahdali dynasty, when he stayed at the court of al-Hasan ibn Sulaiman Abu'l-Mawahib [ruled 1310-1333]. It was during this period that the major architectural constructions were made, including elaborations of the Great Mosque and the construction of the palace complex of Husuni Kubwa and the market of Husuni Ndogo.

The prosperity of the port city remained intact until the last decades of the 14th century when turmoil over the ravages of the Black Death took its toll on international trade. By the early decades of the 15th century, new stone houses and mosques were being built up in Kilwa. In 1500, Portuguese explorer Pedro Alvares Cabral visited Kilwa and reported seeing houses made of coral stone, including the ruler's 100-room palace, of Islamic Middle Eastern design.

The dominance of the Swahili coastal towns over maritime trade ended with the arrival of the Portuguese, who reoriented international trade towards western Europe and the Mediterranean.

Archaeological Studies at Kilwa

Archaeologists became interested in Kilwa because of two 16th century histories about the site, including the Kilwa Chronicle. Excavators in the 1950s included James Kirkman and Neville Chittick, from the British Institute in Eastern Africa.

Archaeological investigations at the site began in earnest in 1955, and the site and its sister port Songo Mnara were named UNESCO World Heritage site in 1981.