Our shop area in Schweinfurt was built on an old Luftwaffe airdrome , and they had rubber "skirts" about 5 inches high around the entire perimeter of the unevenly shaped runways. We couldn't figure out what they were for, so we asked some of the older people from the area, and they said that during air raids, they would flood the runways with about 4 inches of water. From 30,000 feet in the air, it looked like a pond or lake. We also found the drains,pumps, and storage tanks for all that water while doing p/m's on some of the base equipment one day. what a mess.....