Bratislava played host to an urbanism conference called Start with Children this week. The Slovak capital’s mayor, Matus Vallo, had pushed to organise the event because he’s ambitious about delivering change to this city of some 425,000 souls. But he also wants Bratislava to lead, to be known for something that will stand the test of time. “We’re never going to be famous for our food because most of it was invented in Vienna,” he said, referring to his nation’s time as part of the Austro-Hungarian empire. “And we’re not going to be famous for our statues or monuments when Prague and Budapest are nearby,” he told the audience – only half-jokingly. Putting children at the heart of urban planning could be something that the city comes to own.I first met Vallo a few years ago at an event in Prague, then did a story on his work as mayor and, finally, dragged him along to The Monocle Quality of Life Conference in Munich as a speaker, where he was a hit: straightforward, passionate, good trainers. His career as an architect and rock-band member only adds to the effect that he has. So when he asked whether I would host a session at his summit, I was happy to return, especially when my line-up of panellists would include the mayors of Warsaw, Gdansk and Tirana, the deputy mayor of Reykjavik, and, of course, Vallo.The event was held inside the restored, old market hall and was packed with some 600 people who came to hear from practitioners and leaders from around the world. Danish architect and planner Jan Gehl, now 87, was in conversation with Amanda Burden, former New York planning commissioner and now principal at Bloomberg Associates. They received the sort of welcome usually reserved for popstars. Speaker after speaker made the argument that if you design streets where children feel safe, everyone feels safe. If you calm and remove traffic to protect youngsters, we all gain from it.But it’s not that simple. Taking parking spaces away and inserting more bicycle lanes has the ability to polarise people, provoking anger and mayhem. As one of the speakers said, everyone is up for change as long as it doesn’t involve them changing. And this is where the children come in because, when the debate is dropped to knee-height, you can start building consensus – well, sometimes. When you remove the risk of a child being killed by a car, diminish the chance of them suffering from asthma, then the debate becomes easier.