A few hours out of Adelaide, near the town of Orroroo, there’s a hill where cars roll up, not down. Or at least, that’s what the sign says. Every year, countless tourists turn up to try out the phenomenon. They switch their cars into neutral and freak the kids out as they gently roll up the hill. But it’s all an illusion created by the locals to fool the tourists. So how does this illusion work and should you tell the kids the truth - or just enjoy the surprised silence as you roll up the hill?