In the early 1930s, American engineers confronting the construction of Hoover Dam discovered that the very material meant to hold back the Colorado River could destroy itself from within — concrete, in sufficient mass, generates heat enough to crack and crumble over a century of slow cooling. Their answer was a quiet revolution in thinking: rather than pour one great monolith, they built 215 separate columns, threaded with 582 miles of cooling pipe and chilled by a plant producing a thousand tons of ice each day, then grouted the whole into unity. The dam stands today as both an engineering la