DJENNÉ, Mali — As in so much of the Islamic world, “insha’Allah” — “if God wills it” — is how people punctuate conversations in this predominantly Muslim West African country. If you speak of starting a project, or taking a trip, or trying to pay a debt, the outcome is always understood to be conditional.


Recently Malians have had to trust heaven more than usual. The year’s millet crop arrived too early and much too thin. In late fall and winter there were attacks on Europeans by a Qaeda affiliate. The military overthrow of the government in Bamako, the nation’s capital, left one of Africa’s poorest nations shut off from the world. Meanwhile Tuareg rebels and Islamist forces have seized the northern half of the country, including Timbuktu.


Tourism, so vital to the economy, has been reduced to a trickle, though West Africa has never attracted the kind of monument-hungry crowds that flood into Egypt. Most travelers who come here are in search of “black” Africa — the Africa of so-called tribal art — and many are only dimly aware of the extraordinary vitality of Islamic culture, old and new, below the Sahara.


In modern cities like Bamako, and Dakar in Senegal, this culture often assumes a pop voice, with religious phrases spray-painted across walls and devotional music pounding and keening over the airwaves. In the ancient pilgrimage city of Djenné, set between two rivers in the country’s center and accessible only by ferry, the voice is quieter, tempered by tradition, but also shaped and, some would say, distorted, by modern intervention.


Djenné, along with Timbuktu, was long a central point for the diffusion of Islam deep into the continent. Although Islam took firm hold in the city only in the 13th century, when a local ruler converted, it had been filtering in on trade routes from the Mediterranean coast and the Middle East for centuries. Along with salt, gold and slaves, merchant caravans brought scholars and scribes, many of whom stopped along the road to set up Koranic schools and manuscript ateliers.


Their path can still be imagined today in the countless small village mosques that dot Mali’s landscape like way stations, some squat and foursquare and painted candy-box turquoise and white, others molded from earth like ceramic pots. And it’s easy to experience the age-old thrill of arriving at Djenné itself, with its majestic Great Mosque seen from afar against the horizon, dwarfing the city around it.


 The mosque is one of Africa’s most revered religious monuments. Constructed almost entirely from sun-dried mud bricks coated with clay, it is the largest surviving example of a distinctive style of African architecture. In tribute to its status, it has been designated, together with its immediate neighborhood of low-rise adobe houses, as a Unesco World Heritage Site.


Yet for a Western viewer the Unesco seal of approval  may raise expectations that the building doesn’t quite meet. Heritage implies great age, and the mosque, as it now exists, is not ancient. The original mosque, dating from the 13th or 14th century, was a ruin when a French explorer reported seeing it in 1828, and was later demolished. It was only in 1907, by which time Djenné had become a French colonial outpost, that the mosque we see today was constructed on the site of the first one.


The architect, Ismaila Traoré,  the city’s chief mason and a Muslim, used traditional materials, including the palm-trunk inserts that bristle from the facade. But as historians have noted, the overall design adheres to the neo-Sudanese style being promoted at the time by the French, who wanted to give a uniform look to all their West African properties.


Even if you accept the 1907 mosque as the new “original,” heritage-worthy in its own way, on the order of the Cathedral of Notre-Dame in Paris, problems arise, because the building is still changing. The climate in Mali — long hot, dry stretches broken by torrential rains — is rough on mud-brick architecture. Fissures and leaks quickly develop and grow. So every year since the Great Mosque was built, it has required a mud replastering, which the citizens of Djenné undertake as a festival event called the Crepissage de la Grand Mosquée.