I'm surprised that the German High Command didn't figure out that Normandy was the best potential spot for an allied invasion force to land in Europe. After all, Saxon England was invaded from bases in Normandy in 1066 by William, Duke of Normandy; how much more information like that did the GHC need to realise that one day, the British could pay a return visit? When Rommel was put in charge of the Normandy sector of the Atlantic Wall, he realised that this was a distinct possibility, and started building up defences in the area at a rapid rate. If you want to know some of the strategems the Allies used to fox the Germans in June '44, get hold of a copy of the book 'The Dambusters' by Paul Brickhill--in that regard it's very interesting...
Apropos to the above post regarding a Channel Tunnel from southern Britain to Pas de Calais, I'm surprised that it didn't cross Hitler's mind. He had millions of potential slaves to use in the construction project, and would have had no qualms at all about working them to death to get the tunnel built as quickly as possible. After the failure of the German effort in the Battle of Britain, and the cancellation of Operation Sea Lion, and particularly after Pearl Harbour pushed America into the War, he must have known that he had only a few years grace before the Allies became strong enough to launch an invasion of the Continent.