The city of Angkor in what is now Cambodia has long been known as one of the world's great former cities. However, just how large it was at its peak has remained debated, with most of the city reclaimed by the jungle and its extent unclear. A new study indicates that at its height in the 13th century, Angkor housed 10 times as many people as London at the same time, far exceeding any contemporary European city.
The Khmer Empire (802 CE to 1431 CE), ruled from Angkor, covered modern-day Cambodia, Laos, and much of Thailand and Vietnam. European visitors to southeast Asia were astonished by the scale of Angkor Wat, the immense temple at the city's heart, thought to be the largest religious structure by land area in the world. They used various methods to attempt to estimate how many people once lived around it. Their techniques were unreliable, however, and came up with wildly diverging figures. The process has continued since, interrupted by the challenges of visiting the area during the Khmer Rouge (1951 –1999) horrors and the civil war that followed.
Dr Sarah Klassen of the University of British Columbia has taken up the task, using modern technology such as helicopter-mounted lidar to expand our knowledge of the city's changing extent, along with traditional archaeological excavation data, to present the first model of demographic growth in Angkor.
“Estimating Angkor’s population has been an enduring challenge, as conventional methods for estimating population size and density in urban areas are not easily applied at Angkor, where nonreligious architecture was composed almost entirely of organic materials that decayed centuries ago, leaving no structural remains,” Klassen and co-authors write in Science Advances.
However, by seeking more subtle traces of human habitation Klassen and co-authors believe they have established the city's boundaries at different times. Combining these with density estimates they conclude the greater Angkor area, including what we might now call suburbs, held 700,000-900,000 people between 1180 and 1300, the city's peak.
For comparison, London was home to just 80,000 people at the end of this time, and for most of Angkor's prime was considerably smaller. Other great European cities were larger, but estimates place even the greatest at between quarter to half of Angkor's size. It is likely to have been the most populous city in the world at the time by a long way.
Around 160,000 people lived in the densely packed civic-ceremonial center, with the rest in the much larger Angkor metropolitan area and embankments. The city sprawled over some 3,000 square kilometers (1,200 square miles), allowing much of its food to be grown in the outer reaches. The authors acknowledge the size of the city's economic catchment area is not known.
The causes of Angkor's decline are even more heavily debated than its peak size, but disease and changes to the monsoon season probably contributed, along with failures to keep up the irrigation system on which the city depended. This allowed the Khmers to fall under the power of the neighboring Siamese empire, who sacked Angkor in retribution for a revolt in 1431, leading to most of its citizens abandoning the city.