Imagine a wall of water three stories high traveling at highway speed, wiping entire towns off the map and creating inland lakes the size of small countries. This is the 1975 Banqiao Dam failure in Henan, China, a catastrophe so immense it forced a nation to bomb its own infrastructure, yet it stayed hidden from the world for decades.

This episode traces how the so-called invincible Iron Dam collapsed during Typhoon Nina, killing somewhere between 26,000 and 240,000 people. We unpack the collision of flawed Soviet engineering, a silenced whistleblower, deforestation, bureaucratic denial, and political secrecy that turned a storm into the ultimate man-made disaster, and ask whether modern mega-projects are repeating the same blind faith.

• How Soviet design obsessed with retaining water left the dam with too few sluice gates and no  ...