Chan Chan

The largest mud-brick city on Earth, on the danger list since 1986

Chan Chan, at the mouth of the Moche Valley five kilometres west of Trujillo on Peru's northern coast, was the largest earthen city of the pre-Columbian Americas. It was the capital of Chimor, the kingdom of the Chimú, who rose along this desert shore around AD 900. At its height the city covered some 20 square kilometres around a dense core of six, and was home to perhaps 40,000 to 60,000 people.

Almost no rain falls here, so everything depended on water from the Andes. The Chimú, called by one hydraulic engineer the first true engineering society in the New World, ran an irrigation system fed by the Moche and Chicama rivers through a canal some 80 kilometres long, which let them thrive in a desert valley. Their capital was built to a strict plan. Its monumental heart holds nine great rectangular citadels, or palaces, each enclosed by high, thick earthen walls, with temples, dwellings, storehouses, reservoirs and funerary platforms arranged around open plazas. Each new king built his own compound and was buried in it with members of his retinue. Around the citadels lay smaller compounds and workshop quarters for weaving, woodwork and metalwork, where artisans lived in small, crowded rooms.

The walls are decorated with friezes of abstract patterns, human figures and animals. In the Tschudi complex, the only citadel open to visitors, rows of fish swim north and south across the reliefs, read by some as the two currents off the coast, the cold Humboldt and the warm El Niño. Its walls rise as high as twelve metres, five metres thick at the base and one at the top, an apparent precaution against earthquakes.

The Inca conquered the Chimú around 1470, scattering many of their people across the empire, and Chan Chan declined. In 1535 Francisco Pizarro founded Trujillo nearby, and the Spaniards looted the burial platforms; one 16th-century list records treasure worth 80,000 pesos of gold taken from a single tomb. Recently archaeologists made what one scholar called the discovery of the decade: an almost intact elite burial platform in the Utzh An complex, its main chamber sealed for nearly 600 years, with at least 38 people buried among metal weapons, gold and copper and textiles.

UNESCO listed Chan Chan in 1986 and at once placed it on the List of World Heritage in Danger, where it has stayed. Mud brick is fragile. El Niño storms bring heavy rain and flooding that eat at the base of the walls, and illegal farming and urban sprawl press in, while Peru's Ministry of Culture works to conserve the walls with the same earthen materials the Chimú used.