Djinguereber Mosque, Timbuktu

The richest man, and his city

In 1324 the ruler of the Mali Empire, Mansa Musa, set out across the Sahara on pilgrimage to Mecca with a famously vast entourage and a famously vast quantity of gold.

His spending in Cairo on the way, gifts and purchases on such a scale, is said to have depressed the value of gold in Egypt for years afterward. The story made Mali, and its desert trading city of Timbuktu, legendary across the medieval world, and put them on European maps: a century later a Catalan atlas drew Mansa Musa enthroned, holding a golden nugget.

On his return, around 1327, Mansa Musa set about building. The greatest result was the Djinguereber Mosque.

A cathedral of mud

The mosque is one of the masterpieces of Sudano-Sahelian architecture, and it is built, almost entirely, of earth.

Its walls are mud brick rendered in smooth earth plaster, its roof carried on rows of heavy pillars, its minaret a tapering pyramid. The most striking feature is the toron: bundles of palm-wood beams left permanently projecting from the walls. They are not decoration. Mud buildings must be re-plastered every year after the rains, and the toron are the built-in scaffold the whole community climbs to do it; the mosque is, in a sense, repaired by hand forever.

Tradition says it was designed by al-Sahili, a poet and architect Mansa Musa is supposed to have brought back from Arabia. Today historians are sceptical: the style is rooted in much older Saharan and West African building, and the foreign-genius story probably gives too little credit to local masons.

Gold one way, salt the other

Timbuktu existed because of two things that meet there: gold and salt.

Gold came up from the forest kingdoms to the south. Salt (essential, and scarce in the Sahel) came down from mines deep in the Sahara, at places like Taghaza, cut into great slabs and carried by camel caravan across the desert. In the markets of the Sahel the two were sometimes traded close to weight for weight. The caravans that crossed the sand also carried copper, cloth, and books, and the tolls on this trade are what made Mali, and its mansa, so rich.

A city of books

Timbuktu's deeper fame was not gold but learning.

Around its mosques (Djinguereber, Sankore, Sidi Yahya) grew one of the great centres of scholarship in the medieval Islamic world, sometimes called the University of Timbuktu. Students came to study the Qur'an, law, grammar, astronomy and medicine. The city accumulated tens of thousands of manuscripts, copied and traded and handed down in private family libraries.

Many survive. In 2012, when armed groups occupied the city and threatened to destroy them, residents and librarians smuggled hundreds of thousands of manuscripts out of Timbuktu to safety: a rescue, seven centuries on, of the thing the city was really built around.