In 2007, an international team of researchers using satellite photographs and other modern techniques concluded that Angkor had been the largest pre-industrial city in the world, with an elaborate infrastructure system connecting an urban sprawl of at least to the well-known temples at its core. Angkor is considered to be a "hydraulic city" because it had a complicated water management network, which was used for systematically stabilizing, storing, and dispersing water throughout the area. This network is believed to have been used for irrigation in order to offset the unpredictable monsoon season and to also support the increasing population. Although the size of its population remains a topic of research and debate, newly identified agricultural systems in the Angkor area may have supported between 750,000 and one million people.