What are the large concrete artifacts, are they remains of MULBERRY?
Yes, those are the remains of Mulberry. I had the opportunity to visit the DDay beaches in 1987. While I was in Arromanches where the floating harbor was, I met a man from Scotland that had driven the amphibious Ducks shuttling materials from the ships up onto the shore. Listening to his description of the harbor in action was fascinating as we were standing high above the bay where the Germans had their guns situated.
To be able to visualize everything helped to me to gain a better grasp of the magnitude of the undertaking. The Phoenix floating breakwalls were designed to last 4 years. There were still about 15 of them visible
in the distance when I visited.