case of the concrete crazies

So I went to Cape May, NJ last week with three friends. Well, first we went to Wildwood, NJ to participate in the Polar Bear Plunge. Then we went to Cape May. Anyway, on the beach at Cape May we saw this huge crazy concrete structure just sitting on the beach, on the edge of land and water. It had no tresspassing signs all over it. When you walked around the side of it closest to the water you could crawl under it. That's how I got this picture. I really like this one. Especially the paths of light and dark. Anyway again, does anyone know anything about this structure?