Why is Berlin special?

Why is Berlin special? Certainly not for its beauty or its state of preservation. Berlin is fascinating rather, as a city of bold gestures and startling incongruities, of ferment and destruction. It is a city whose buildings, ruins, and voids groan under the burden of painful memories […] The concentration of troubling memories, physical destruction, and renewal has made Berliners, however reluctantly, international leaders in exploring the links between urban form, historical preservation and national identity.