The purpose of this slick and engaging (and often terrifying) documentary is to remind us of the fact that the worst danger of the cold war did not die with the death of that long ideological battle, capitalism vs. communism. Even today, 20 years after the fall of the Berlin Wall, humanity is still caught in the teeth of nuclear weapons. At any moment, the human world could go up in smoke. At any moment, millions of lives could be dispatched to the other world by an atomic weapon whose uranium was purchased on the black market and whose parts were assembled by a God-intoxicated scientist.

The documentary is not about the destruction of nations but the destruction of cities, and specifically the king of all cities, New York, New York. The director, Lucy Walker, sees the very city that played a major role in translating the secrets of atomic energy into atomic weapons (The Manhattan Project) as the one that's currently in the most danger of being annihilated by that terrible power—the power of nuclear fission, the power of a sun. One scene demonstrates how uranium can arrive at a port, pass detection, be transported to the center of Manhattan, be placed into a bomb that's been assembled in a basement, and be detonated. In a blinding flash, millions of American lives are dispatched to the other world (if there is another world—most likely there is nothing but nothingness).

The nuclear threat is, first and foremost, a threat against dense urban centers—Rome, San Francisco, Shanghai, London, Moscow, Paris, Tokyo, São Paulo. Every city remembers Hiroshima—the first city of the 20th century. (It's important to note that Walker has also recently completed a documentary, Waste Land, about the creative side of another form of urban destruction—humans' garbage.) You do not drop a nuclear bomb on the countryside; you drop it on a place that has lots and lots of human lives. The arrival of the most powerful weapon on earth corresponds with the accelerated urbanization of humanity. The worst of all worlds came with the best of all worlds. Indeed, the director's emphasis on the terrifying vulnerability of cities recalls something that the Dutch urban theorist Saskia Sassen recently pointed out: "Something about destroying a city has a much deeper meaning than just death."