Melvyn Bragg presents the first of a two-part discussion about the history of the city. With Peter Hall, Julia Merritt and Greg Woolf.The story of cities is widely held to begin in the 8th millennium BC in Mesopotamia. By 4000 BC, there were cities in the Indus Valley, by 3000 BC in Egypt, and by 2000 BC in China. What happened in the west was the furthest ripple of that phenomenon. In 1000 BC Athens still only had a population of one thousand. At its height, Athens' position as a powerful Mediterranean trading city allowed it to become the birthplace of much that would later characterise western cities, from politics through architecture to culture. Then, early in the first millenium AD, the world saw its first million-strong city: Rome. Maintaining a population of this size required stupendous feats of organisation and ingenuity. But in following centuries, as Rome declined and fell, the city itself, in the west at least, declined too; power emanated from kings and their mobile courts, rather than particular settlements.In China, urban trading posts continued to flourish, but their innovative energy dwindled before the end of the first millennium. Between 1150 and the onset of the Black Death in 1350, the city underwent a resurgence in Europe. City-states developed in Italy and in Germany. At this stage, there was no omnipotent power-centre to match Ancient Rome. But with the growth of sea and then ocean trade, and the centralisation of power in capitals ruling nation-states, cities like London, Paris, Madrid, Amsterdam and St Petersburg became increasingly wealthy, dynamic and ostentatious. By 1801, one of these - London - finally matched Ancient Rome's peak population of a million. Along the way, the city had become an ideal to be revered and a spectre to be feared.Peter Hall is Professor of Planning and Regeneration at The Bartlett School of Planning, University College London; Julia Merritt is Associate Professor of History at the University of Nottingham; Greg Woolfis Professor of Ancient History at the University of St Andrews.