Dynastic History|The Great Mosque of Kilwa — Coral, Lime and Three Campaigns

The traveller Ibn Battuta reached Kilwa in 1331 — a date some scholars place a year or two earlier — and described its mosque, though the Rihla was dictated to Ibn Juzayy more than two decades after the journey and gets parts of the building wrong. What he saw was already the work of several generations. The northern prayer hall came first, in the eleventh or twelfth century: sixteen bays under a flat roof carried on nine columns cut from coral, later replaced in timber.

Coral was the technology of the whole coast. Reef blocks were quarried at low tide, burnt in kilns for lime, laid as rubble and rendered smooth; mangrove poles from the creeks spanned what stone could not. No chronicle names the quarriers, the lime-burners or the crews who moved the stone by boat. That labour is legible only in the fabric.

Sultan al-Hasan ibn Sulaiman extended the mosque southwards early in the fourteenth century and roofed part of it with a dome, which architectural historians have called the first true dome on this coast. It did not last. The hall a visitor walks through today is a rebuilding of the first half of the fifteenth century, attributed to the reign of Sulaiman ibn Muhammad, about 1421 to 1442: some thirty bays under barrel vaults and low domes of coral-lime concrete twenty to thirty centimetres thick, at that point the largest roofed mosque on the East African coast. The building went out of use in the eighteenth century.

The ruins stand on Kilwa Kisiwani, a short boat crossing from Kilwa Masoko. Tanzania's antiquities authorities manage the site, inscribed by UNESCO in 1981 and on its danger list from 2004 until 2014.

📸 Cover: The vaulted southern hall of the Great Mosque of Kilwa, Richard Mortel, CC BY 2.0 via Wikimedia Commons