The Mulberry Harbors: Engineering Marvels of D-Day

The Allies created two massive artificial harbors (Mulberry A at Omaha Beach, Mulberry B at Arromanches) by towing 115 massive concrete caissons — each the size of a small building — across the English Channel. Each caisson weighed up to 6,000 tons. They sank them in place to create breakwaters, then built floating roadways with articulated bridges that flexed with the tides. Mulberry A was destroyed by a storm on June 19 but Mulberry B operated for 10 months, unloading 2.5 million men, 500,000 vehicles, and 4 million tons of supplies. Remnants of the Mulberry B harbor are still visible at Arromanches today.