During the invasion of Normandy in 1944 the allied forces needed a way to get supplies and troops moving inland once they had taken the beach, post d-day. The set up a series of floating harbors and bridges called "Mulberries". Most of them dont exist anymore but near Arrowmanches on the french cost between Omaha and Gold beaches you can still see them at low tide, they are now sunk into the floor of the channel. It was really neat!
We also went to the 360 museum at Arromanches which was a film shown in a circular theater about what the soldiers landing in Normandy would have experienced on that day. It was a really cool experience, although it made me a little but dizzy!