A "moonbow" is one of nature's rarest sights – and Victoria Falls is one of the few places on Earth where travellers might catch it. The first thing I noticed was not the darkness, but the sound. It began as a low, distant rumble, easy to mistake for wind. But as the path narrowed and the trees thinned, the noise deepened into something more primal, swelling into a relentless roar that pressed against my chest. By the time I reached the edge of the waterfall, the sound was no longer just