At the end of the first millennium, the only city that came close to reaching one million inhabitants was Baghdad — an incredible feat considering the total world population was estimated to be about 230 million. Fast-forward one thousand years to 1950. With the world population at 2.5 billion, the planet witnessed the rise of its first megacities — urban conglomerations of more than ten million inhabitants. The first of these colossi were Tokyo and the New York/Newark urban region. Today, there are 29 megacities, the majority in the developing world. By 2030, this number is expected to rise to 41. But, urbanisation isn’t just producing megacities. More than 50% of the world’s population now lives in cities of all sizes, with the figure projected to reach 85% by 2100. Within 150 years, the urban population will have increased from less than 1 billion in 1950 to 9 billion by 2100.