Kilwa Kisiwani: Medieval Trade Center on Africa's Swahili Coast

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 the Swahili Coast sites conducted an active trade between interior Africa and the Indian Ocean during the 11th through 16th centuries CE.

Key Takeaways: Kilwa Kisiwani

  • Kilwa Kisiwani was a regional center of the medieval trading civilization located along the Swahili Coast of Africa.
  • Between the 12th and 15th centuries CE, it was a principal port of international trade in the Indian Ocean. 
  • Kilwa's permanent architecture included maritime causeways and ports, mosques, and the uniquely Swahili warehouse/meeting place/status symbol called "stonehouses." 
  • Kilwa was visited by the Arab traveler Ibn Battuta in 1331, who stayed at the sultan's palace. 

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 the Mwene Mutabe societies 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 CE 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, albeit in a relatively small way. Evidence shows that the people living at Kilwa and the other towns were involved in some trade, localized fishing, and boat use.

Historical documents such as the Kilwa Chronicle report that the city began to thrive under the founding Shirazi dynasty of sultans.

Growth of Kilwa

Sunken Courtyard of Husuni Kubwa, Kilwa Kisiwani
Sunken Courtyard of Husuni Kubwa, Kilwa Kisiwani. Stephanie Wynne-Jones/Jeffrey Fleisher, 2011

Kilwa's growth and development around the beginning of the second millennium CE was part and parcel of the Swahili coast societies becoming a truly maritime economy. Starting in the 11th century, the residents began deep-sea fishing for sharks and tuna, and slowly widened their connection to international trade with long voyages and marine architecture for facilitating ship traffic.

The earliest stone structures were built as early as 1000 CE, and soon the town covered 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 such as the Palace of Husuni Kubwa. Kilwa rose to its first importance as a major trade center about 1200 CE 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

Bathing Pool at Husuni Kubwa, Kilwa Kisiwani
Bathing Pool at Husuni Kubwa, Kilwa Kisiwani. Stephanie Wynne-Jones/Jeffrey Fleisher, 2011

The constructions built at Kilwa beginning in the 11th century CE were masterpieces built of different types of coral mortared with lime. These buildings included stone houses, mosques, warehouses, palaces, and causeways—maritime architecture that facilitated docking ships. 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; and combined with sand or earth to make a mortar.

The lime was burned in pits using mangrove wood until it produced calcined lumps, then it was processed into damp putty and left to ripen for six months, letting the rain and groundwater dissolve the 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

Kilwa Kisiwani, Aerial View
Aerial view of stone ruins at Kilwa Kisiwani, Swahili coast, Tanzania.  Paul Joynson Hicks / AWL Images / Getty Images

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 revealed that what appears to be an empty space between the two areas was at one time filled with lots of 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.

Causeways

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 650 feet (200 meters) and in width between 23–40 ft (7–12 m). 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 their 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 built, including elaborations of the Great Mosque and the construction of the palace complex of Husuni Kubwa and the market of Husuni Ndogo.

Kilwa Kisiwani (Quiloa) - undated Portugueuse map, published in Civitates Orbis Terrarum in 1572
Kilwa Kisiwani (Quiloa) - undated Portugueuse map, published in Civitates Orbis Terrarum in 1572. Hebrew University of Jerusalem

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. more recent studies have been led by Stephanie Wynne-Jones at the University of York and Jeffrey Fleischer at Rice University.

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.

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