You know, there isn't a single empire, no matter how evil or backward, that didn't at least make SOME positive contribution to mankind. If nothing else, Christian and Muslim religious fanatics gave us wonderful architecture. The Soviet Union launched the Sputnik. And so on. Even the Italian fascists had Ezra Pound.
The one exception is the Nazis. They had no worthwhile architects (Speer's megalomaniacal nonsense doesn't count), philosophers, writers, poets, scientists, artists, or anything. Even the famous autobahns, or "Fuhrer roads", were Potemkin villages: created mostly for show and to reduce unemployment, and partially (duh) using slave labor of Jews and other undesireables, these roads were practically empty, as the vast majority of Germans were, as usual, lied to by the Nazis who said they could get cars under the new Reich.
All we are left with are a few fantasy super-weapons (big surprise there -- the Nazis tunneling most of the creative energy they had, such as it was, towards making killing machines, whether weapons or gas chambers): mostly of airplanes, but also all kinds of super-weapons such as a a 1000-ton tank, 100-mile-range cannons, and so on.
All of these looked really cool on paper, but, like most of what the Nazis said, wrote, and did, is pathetically adolescent in its outlook: these designs show us designers obsesses with "cool looking" and "fastest / heaviest / strongest / longest range" machines, like 15-year-olds upgrading their spaceship in the latest computer game, being totally oblivious to understanding the difference between fanciful designs and actual practical production. Needless to say, none of these "super-advanced" machines were ever built by the Americans or Soviets which laid their hands on the plans when the war ended. Then again, the people who ran their weapons programs might have been many things, but not permanently adolescent fantasists, like most Nazis, up to and including Der Fuhrer.
The only things left of their legacy today are -- as Michael Burleigh noted -- a few colossal concrete bunkers, too big to blow up, torture chambers, wind-swept parade grounds, rotting wooden huts, and the concentration and extermination camps. There is NOTHING positive AT ALL to show for all those mountains of dead -- a negative achievement unique in the history of mankind.
