Left click and hold on each photo, and then drag your mouse gently from left to right on the original photograph and it will be become a photo of the exact same location as viewed today - drag it back to the left and you are back in 1944!
Scroll down for more of the same. Just fascinating!
http://interactive.guim.co.uk/embed/2014/apr/image-opacity-slider-master/index.html?ww2-dday