For his talk “The 21st-century Medieval City,” Robert Neuwirth took an overflow audience to “the cities of tomorrow,” the developing-world shanty-towns where a billion people live now, and three billion (a third of humanity) are expected to be living by 2050. With vivid stories and slides (shown for the first time publicly), Neuwirth detailed how life works for the squatters in Rio, Nairobi, Istanbul, and Mumbai. It’s hard for new arrivals – 1.4 million a week around the world, 70 million a year. They throw together mud huts and make do with no water, no electricity, no transportation, no sewage, and barely room to turn around amid square miles of dense crowding.