Mulberry Harbour was a system of floating docks used by the Allies (who were fighting in World War II) to land troops and equipment on the coast of France during D-Day (June 6, 1944). It was built so that the Allies could get their ships close enough to the beach to unload the troops and materials, without the ships getting destroyed by enemy fire. It was made of floating steel and concrete so it stayed afloat in the water, and it was covered with soil and plants so it would look like a natural part of the French coastline. It allowed the Allies to land their troops and tanks safely, and it was a critical part of the victory that they achieved during World War II.