The largest Pre-Columbian city in South America, Chan Chan is an archaeological site located in the Peruvian region of La Libertad, five km west of Trujillo. Chan Chan covers an area of approximately 20 km² and had a dense urban center of about 6 km². Chan Chan was constructed by the Chimor, a late intermediate period civilization which grew out of the remnants of the Moche civilization.
The vast adobe city of Chan Chan was built by the Chimu around AD 850 and lasted until its conquest by the Inca Empire in AD 1470. It was the imperial capital of the Chimor until it was conquered in the 15th century. It is estimated that around 30,000 people lived in the city of Chan Chan. Chan Chan was added as a UNESCO World Heritage Site in 1986. The city is severely threatened by storms from El Niño, which cause heavy rains and flooding on the Peruvian coast. It is in a fertile, well-watered section of the coastal plain.
The city's ruins are additionally threatened by earthquakes and looters. Present-day visitors to Chan Chan can enter the Tschudi Complex, believed to be one of the later citadels built in the city. There are also several other Chimú and Moche ruins in the area around Trujillo. This site was discovered by the Conquistador Francisco Pizarro.
The city is composed of ten walled citadels which housed ceremonial rooms, burial chambers, temples, reservoirs and some residences. Chan Chan is a triangular city surrounded by walls 50–60 feet high. A distinguishable aspect of Chan Chan is that there are no enclosures which open to the north.
The tallest walls shelter against south-westerly winds from Peru's coast. Northern-facing walls gain the greatest exposure to the sun, serving both to block the wind and absorb sunlight where fog is frequent. The numerous walls throughout the city create a labyrinth of passages.
In order to increase the amount of farmland surrounding the city, a vast network of canals that diverted water from the Moche river into the area around the city was installed. It was only with the construction of these canals that the city's population could increase. Before the canals were dug, the city relied on a number of wells that were dug up to 15 meters into the ground.
Many of the canals to the north of the city were destroyed by a catastrophic flood in c. 1100 AD, which was likely the key motivation for a need for the Chimú to refocus their economy towards one rooted in foreign resources rather than subsistence farming.
As the world's largest adobe city, the ancient structures of Chan Chan are today threatened by erosion due to changes in weather patterns - heavy rains, flooding, strong winds.