IN A NUTSHELL 🌊 The Metropolitan Area Outer Underground Discharge Channel is the world’s largest underground flood protection system, stretching over 3.7 miles beneath Kasukabe. 🏗️ Built between 1993 and 2006 at a cost of over $1 billion, this engineering marvel protects Tokyo from extreme rainfall by diverting floodwater to the Edo River. 🌧️ With … Continue reading “268 Olympic Pools Below Ground”: World’s Largest Hidden Reservoir Discovered in Shocking Subterranean Water Breakthrough