I didn't get around to writing about D-Day yesterday, on its 72nd anniversary, as I was away from home most of the day. A shopping trip in western Wyoming often involves driving 200 miles. Not complaining, just saying....
The other DrC and I visited Normandy a few years back and toured the invasion beaches and German fortifications. Omaha Beach is particularly striking, as is Pont du Hoc.
At Omaha it was abundantly clear to the Germans what route the Allies would have to take to bring vehicles up off the beach. Mostly in that area the beach is backed by a cliff that is perhaps 30-40 ft. high, the one access road inland runs up a small valley that the Germans heavily fortified and mined.
Another thing that remains is the man-made harbor that sprang up on an otherwise bland coastline. Brits created gigantic concrete boxes that would float, towed them across the Channel, and sank them in shallow water to produce a protected area within which unloading could continue regardless of how rough the seas got in the Channel. They also sank rusty old hulks to complete the encirclement. The concrete boxes, called "mulberries," are still there 70+ years later.
While in Normandy, you'll probably go to the D-Day Museum which is excellent. Also see the Bayeau tapestry which is displayed nearby, it's historic and interesting even if it doesn't look much like what you think a tapestry should resemble. Think of it as a 200+ ft. long cartoon, done on fabric, depicting the sequential steps by which the Norman invasion of England occurred in 1066.