Kilwa

Three places share the name. Kilwa Kisiwani is the island, and the ruins — a UNESCO World Heritage Site since 1981. Kilwa Kivinje is the nineteenth-century mainland town that replaced it. Kilwa Masoko is the modern district centre where you sleep and where the boats leave from.

The island settlement was founded at the start of the 9th century, on carbon dating, and by the thirteenth had done something remarkable: it seized control of the gold trade out of Sofala, in what is now Mozambique. Gold from the Zimbabwean plateau moved down to the coast and then north through Kilwa's hands to Arabia, Persia, India and China. The town minted its own coins from the 11th to the 14th century, and Kilwa coins have been excavated as far afield as Great Zimbabwe — and, more startlingly, in northern Australia.

At its height the population passed ten thousand and the sultans built in coral stone on a scale nothing else on this coast matched. The Great Mosque, built in the 11th century and considerably enlarged in the 13th, is, in UNESCO's words, the oldest standing mosque on the East African coast, its roof carried entirely on domes and vaults, some set with Chinese porcelain. Husuni Kubwa, built between about 1310 and 1333, was a palace and trading emporium covering some two acres on the cliff above the harbour, with an octagonal bathing pool. It was abandoned before it was finished.

Ibn Battuta stopped here in 1331 and called Kilwa one of the most beautiful cities in the world, praising the sultan's generosity and piety. Less than two centuries later it was gone: a Portuguese fleet under Francisco de Almeida sacked and burned the city in July 1505, and although Portuguese occupation lasted only to 1512, the trade never returned. What stands today is what the forest and the sea left.

Kilwa is Swahili coast in the older sense: overwhelmingly Muslim, unhurried, and organised around the tide and the fishing rather than around visitors. There is no resort strip and no tourist economy of the kind Zanzibar has built, and the difference in how you are treated is noticeable.

Visiting the island is deliberately low-key. You arrange a permit at the Antiquities office in Kilwa Masoko, cross by dhow in about twenty minutes, and walk the site with a local guide. There is rarely anyone else there. Standing inside the Great Mosque with nobody in it is an experience Zanzibar cannot offer at any price, and it is the argument for making the journey south.

Kilwa Kivinje, on the mainland twenty-five kilometres north, is the other half of the story and the sadder one: a nineteenth-century Omani and then German town that ran on the slave and ivory trades, now half-abandoned, with carved doors and collapsing balconies and a German boma on the seafront. It is being lost faster than the older ruins on the island.