The Aztec Empire was the last great civilisation and dominant power of Mesoamerica in the 15th and 16th centuries. By the time the Spanish arrived in 1519, the Aztecs had built an empire covering an area of about 200km2. Its capital city of Tenochtitlan was a huge trading centre and it supported up to 140,000 people, making it the largest city in the Pre-Columbian Americas. Underpinning this empire was its military power of conscripted adult males. Aztec cities boasted temples, palaces and artwork displaying devotion to many gods. They developed sophisticated writing systems, calendars, and a religion that required human sacrifice. Yet their powerful empire would soon be decimated by their encounters with European colonisers and their demise does not just lie in the technological advantages their conquerors had against them.

Founded at the beginning of the 9th century CE, the Khmer Empire had been one of the most powerful states in Southeast Asia, covering much of Cambodia, Thailand, Laos, and Southern Vietnam. The jewel in the crown was the capital city of the Khmer – Angkor – containing the largest religious structure ever built, Angkor Wat. The key to this growth was the Khmer mastery of rice cultivation and water management. Khmer cities were ‘hydraulic cities', made up of complex systems of canals and reservoirs called ‘barays', which steered water from the Khulen mountains to the plains of Angkor, ensuring a year-round supply for the population, agriculture, and livestock. Soon, however, the very factors that allowed the empire to rise lead to the abandonment of the Khmer's magnificent temple-cities and their reclaim by the rainforest.